Paging Delboy... Delboy to the white courtesy phone please | GTAMotorcycle.com

Paging Delboy... Delboy to the white courtesy phone please

Clem

Well-known member
Does anyone know if he still logs in here?

I have a friend building a stroker 421 RZ350 and he wanted to ask him some questions. I sent him a PM before Christmas but no response yet.

TIA
 
He was last on Nov 19. Hopefully he returns. He had lots of interesting things to share.
 
That stroker would be a sweet build. Can you ask your friend to post the progression on the forum?
 
Sorry, OT, but literally the first thing that came to mind. ;)

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Sorry, OT, but literally the first thing that came to mind. ;)

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Ha Ha. I was thinking about that scene when I was posting...

He was looking for some advice on Serval V's Cub, Cranks, Where to get pipes, etc. There are couple of good writeups on line, but they are very generic.
 
rz/rd 350 specific forum...has some 421 builds. good resource.

http://www.rzrd500.com/phpBB3/index.php?sid=623479c4980633cba77da838d40e3929


primer / FAQ :
As the word gets out, more and more people are building larger capacity RD/RZ motors.... of course as you may know from reading this site, I feel that's no bad thing! They offer power and performance from all new parts instead of messing about working on well used (a kind euphemism for 30+ year old worn out) OEM parts. But... There are a lot of options out there and you really do need your wits about you to choose and build one... and honestly no one person has all the answers. So I've created this page as a 'Big Bore Primer' to help those who are thinking about building their own monster motor to gather some grounding in what this subject is all about. I make no claims that it is comprehensive and as time moves on it certainly won’t be complete, but if you are looking to do this work I believe reading it will help you.



Ok, first a few things to get us all on the same page...



Firstly... A bigger cc motor is generally created in two ways, increasing the bore or the stoke, or both. E.g. Adding a +4mm crank to a 66mm bore takes you to 385cc. Adding a 68mm bore to a standard crank is 392cc, adding a +4mm crank to a 68mm bore is 421cc... And so on.



Secondly... All of the larger bore cylinders were created for the Banshee ATV. Many were designed for racers who wanted to drag race (on sand or road) and as such they have either drag porting out of the box, or are quite ‘bare’ when new as they guys who fit them port them themselves, or have their supplier do it. Bear in mind that these guys will spend a lot of money to create a special engine to win races... spending money and racing always go hand in hand.



Thirdly... If you want to fit these units to a road bike, then you really need to do a lot of due diligence and read up and talk to suppliers about the products they sell. Most have never fitted them to a bike, and have no idea about road tunes for use in traffic situations. Many cylinders have large ports that eat rings and need a lot of maintenance as befits a race machine. Always strive get the package that you wanted at the outset; perhaps you didn't really want a peaky drag racer for your daily commute at 7am through city traffic, or a noisy Mx'er’s sound when coming home from the club's night shift?



Finally... Lots of ebay sellers and others websites just on-sell boxed kits that look good value. They may work fine but a specialist who builds engines and works on them will be a better bet than a cheap kit and no after sales backup. After all, you will need to set it up once you have it fitted and a supplier who shrugs and walks away from your questions about airfilters, ignition maps or jetting is going to cost you more money than the initial savings you made on an ‘bargain kit’. Always talk to the supplier and get a feel for what they know before you buy.

Home
What prompted me to do this page was that on the forums there had been a lot of people asking the same questions over and over in different forms, so rather than the same few guys keep answering I tried to write up what is needed in a single place.



So without further ado, here is my FAQ for these ‘big bore’ motors, I hope it will help any prospective builder get a better understanding of what they want/need to move forwards with their project.



Q. Can I go bigger with my old Yamaha 350 cylinders?

A. Yes, you can increase both bore and stroke to add cc's. Standard bore of the OEM cylinders is 64mm, Yamaha will sell you pistons and rings up to 65mm, aftermarket maximum bore is 66mm (some say larger but it leaves a thin wall in the sleeve and potentially cuts into the PVs). Adding a stroked crank will also add capacity, but is a little more involved.



Q. Can I do anything like this with my 250 motor?

A. Well, yes, and the old cylinders make good paperweights. The 250 bottom end will take any of the larger cylinders mentioned here, including the OEM 350s.



Q. How does the stroked crank work?

A. The throw of the crank is longer than standard, so the pistons move up and down a few mm more than OEM, giving a larger cubic capacity.



Q. I can just fit one of those to my old OEM pistons and run it in my motor?

A. No, you need to change the pistons (or use and offset pin) and also you may need to machine the domes to get the fit, squish and compression ration you require. That machining depends on your head and also whether you use 110mm or 115mm rods and as to what pistons you use and all that dictates what profile the domes ned to be machined at.



Q. Can I stroke a 250?

A. What is it with you 250 boys? haha. Ok.... No one has yet stroked a 250, most builders feel that if you’re going to the trouble to build a trick motor then you wouldn’t keep the 250cc to end. One day I might stoke a 250, just to see what it goes like. The OEM standard crank was designed to offset the weight of the 250 pistons, so I reckon it might be a nice revvy machine. Perhaps I’ll report back one day on that.. watch this space...



Q. A supplier suggested I fit a spacer plate but you say I should use offset wrist pins / different pistons, why is that?

A. Honestly, fit new pistons, the spacer plate will effect the port timing and tends to leave a 350 YPVS feeling 'flat' to ride. It’s been done, tested and found wanting...



Q. I’m thinking of ditching my OEM cylinders and getting one of these bigger bore kits on ebay, they seem good value...

A. They are, but you need to read the rest of this page before you get too excited... Don't worry it’s not a nightmare but don't rush into this! Read on...



Q. I just noticed that many of these aftermarket cylinders don't have PVs like my YPVS, how will that work on my YPVS bike?

A. That's right. They are made for the banshee which doesn't have them as it’s an off road ATV and low down tractability for road use is not in its design. You disconnect the YPVS electronics when using these cylinders.



Q. Hmm, No PVs... Doesn't that mean no low down torque and power all at the top end?

A. Well that depends on lots of factors like porting and port/ignition timing and pipes/carb setups but generally I will say that is ‘somewhat incorrect’ as even right out of the box Athena kits don't lack torque, although it may feel so as there is less power low down than there is later in the rev range, but the engine is actually quite powerful low down. This is because the larger cc and port timing will give the low end torque, but yes you will experience the old school burst of power as you hit the powerband, like the LC really, only more so as it’s more powerful than the venerable old LCs sub 40bhp.



Q. Will the bike with these bigger cylinders use more fuel?

A. Yes! If you want an eco friendly engine maybe get a Prius instead?



Q. So, I’m keen... What size is best?

A. If you look at the market you will see most suppliers and kits come in 68mm bore sizes... That's 392cc on a standard crank and 421cc on a +4mm, and of course more if you go longer throw. This is really the entry level of the Banshee upgrade market, hence there are lots of options as suppliers try to get a piece of that action, and yes it does include some cylinders with PVs. Costs vary as does experience by the supplier and bike builders alike.



Q. I’ve seen lots of names out there like Cheetah, Cub, Serval, CPI, TSS, Wicked, Athena and others, what do they mean?

A. Those are manufacturers, resellers and/or products. The market is full of options and it feels like more and more appear ever time you look. The Banshee upgrade market is huge and lots of players want to be part of it. You can fit any/all of them to a YPVS bottom end (but not an LC without work, the cases and studs are different), and they all offer something a bit different. The different names are often subtly different products, some are single casting for the twin cylinders and some are single cylinders. They often use different ports, port timings. Come as kits or just loose parts and some suppliers have designed and had built parts to their own spec of both kits and parts. It’s quite a mine field really...



Q. So what do you suggest I do to get my head round all this?

A. Build what you like/want/need. Sounds obvious, but... My advice is to pick a bhp target and decide how you will use the bike. Talk to suppliers and buy what is right for what you need and your budget. Picking a cc or budget also work, but really the 'need' is about power I suspect... So I would suggest you start there.

N.B. I should add that bhp is not really a measure of performance, a tuned to the 9’s 125 can make as much horsepower but will have a narrow powerband and be useless on the road. So also think about how you will use your bike and if its road use, then I suggest that you sacrifice ultimate bhp for torque.



Q. Hold on, that's not helpful, you didn't answer the question, instead you've just given me homework...

A. Well yes that's true, but what I want (cost and everyday performance with reliability) and what you want might be different... Ok, if you push me, I will say Athena with +4mm crank. It's the most well documented and easy enough conversion to achieve on a budget, with the added plus that plenty of forum guys have now done it. Click this link for my LC421 Athena engine build here, it may help understanding of what’s involved.



Q. Ok, an Athena kit is sub $1000... I can afford that, but what else might I need?

A. When building any uprated motor it’s good practice to first check the rest of the old engine out to be sure it can take what you’re doing as more power will soon flush out / make bigger any issues that are lurking under the surface. Certainly the bearings in the crank and the transmission will need to be good, so budget for gaskets and seals to strip and check that, plus also do an oil and water change. Above that it all depends on what you want again... Assuming you want to get the power unlocked from the motor you will need to invest in exhaust pipes, carbs, airfilters, programmable ignition, thermostat housing / big head, fast flowing fuel tap/filter... And if you really go mad then frame mods, but you can find a compromise of power and fitment to fit all bikes.



Q. But can't I just run big cylinders with standard carbs, ignition and pipes?

A. Well you can, but you wont get the best out of it. You could build on a budget this way for sure, but it won’t be quite as satisfying out of the box. Plenty of guys have just bolted on the Athena kit on their old crank on banshees and ran then hard at 392cc and had fun. Why not give it a go and report what you think on your bike?



Q. Will I need a new electronic ignition?

A. You don't have to, but to get a map that works best with non PV cylinders you may feel its worth it. Zeeltronic or Ignitech are most widely used. you can slot your stator (or buy a slotted stator backing plate) and slip the timing around a bit, while it is what we’d have done in our youth, it’s a bit ghetto for most owners these days.



Q. Should I fit fuel injection?

A. You don't have to, but you could. You would have to make your own setup, and while it’s been done, it’s not documented enough to ‘just do’ yet. At the time of writing, there isn't a kit that is made for our bikes yet, but it will come I expect, Suppliers have talked about it over the years, but unless the banshee market finds it desirable then I suspect we bike guys won’t see it anytime soon as we are too small a market for a big supplier to target.



Q. What exhaust pipes are available for big cc’s?

A. Wicked and TSA are the only ones I know of who do pipes for larger than 350cc for our bikes.



Q. What clutch should I use? will I need one of those ‘locking’ clutches?

A. Well, the minimum you need is a set of uprated clutch springs and with really big cc’s you maybe need the locker, depends on the power. Up to 80bhp standard or uprated with uprated springs will work, above 100bhp that you need to think about lockers to avoid slip.



Q. Should I fit uprated gearbox bearings?

A. I do, but its up to you. The Two Stroke Shop do a kit that is very good.



Q. What about uprated crank bearings?

A. Talk to your supplier about what they suggest. I like to uprate, but not everyone does. Bear in mind that this crank was designed for the 250 engine and not modified for the 350 when Yamaha upped the cc's. So it was already out of balance at 350cc and works hard because of that. Adding more cc's and upping the compression ratio then rev'ing it hard will not endear you to the poor overworked thing. Uprating seems advisable, and balancing (against the actual pistons you will use) seems a good idea if you want it to be smoother, revvier and have a long and happy life.



Q. Should I add straight cut gears?

A. I wouldn't, you don't need them and it adds complexity for no real gain on most motors. If you’re a racer then maybe you will see the need, but for road use it’s not required.



Q. What about cooling, do I need to improve this?

A. Well heat kills 2 stroke motors so yes.... The YPVS has a 450ml rad, the older LC’s was 750ml. A backward step in yamaha’s plan in my eyes for sure. That means in some climates the YPVS was always only just borderline, upping the cc’s and running it harder requires more cooling than what these bikes came with for sure. My advice is that fitting an uprated water pump impeller and larger radiator are a must. Some head setups (the one with the Athena kit for example) don't include a thermostat as the banshee doesn't run one. Wicked sells an aftermarket CNC billet 'cool head' now that is designed for our bikes and comes with the YPVS thermostat with it’s outlet located where it should be for the YPVS/LC (the Athena has the banshee outlet which is different as it sticks straight out the front) and includes the bypass; my advice is to check that head out, it was wholly designed for our installation, none of the others were. Make sure if you buy a big rad that it has the bypass fitting and also is wide enough not to be covered by your suspension (i.e. RGV and other USD upgrades really kill the moving air due to the size of the fork legs, wheel and guard), you may need to add a scoop to get the cold air in in warm climates (search online for oiler's 421, he has built a great scoop for his). To know what's going on, fit a digital gauge (the stand alone Koso is cheap and effective) so you can see what is happening exactly and maybe also add a fan so you can cool it in traffic if you need to. Bear in mind that in a colder climate you may not need all of these mods.



Q. What carbs should I fit?

A. Something like an Athena will run on anything from the OEM 350’s 26mm to massive 39mm carbs. It all depends on what you want, but generally bigger carbs = more power... and also more fuel consumption. Be aware that large carbs are hard to fit in a bike frame, the are often too tall and deep for the chassis/engine, necessitating custom manifolds or bowls and cable angles on the tops and then you need to find filters to fit... They also need fast flowing fuel taps and filters or you may lean out the mixture at high revs. Some guys even add pumps to feed these greedy beasts.



Q. What inlet technology should I use?

A. Some cylinders come with moulded in manifolds, but most just use the OEM fixings and the aftermarket has filled that void with some clever technology. For reeds (rad valve for the ‘muricans’) VForce is well known to work on our bikes, but on smaller motors you could run anything you like of course, including the OEM banshee setup which is cheap and proven to be quite effective on a standard motor. On the larger sizes I would suggest that you go with what your supplier advises. I run VF3s on a Wicked X-over manifold, the manifold allows larger carbs to fit above the clutch actuation lever as well as work better than the standard unit.



Q. Can I fit an oil pump and run autolube or am I stuck on premix?

A. Arrow and TSS both offer uprated pumps, I will be fitting Arrow's version to my 421 soon. Check back for info on that.



Q. Will I need to modify the cases?

A. you will want to match the inlet port transfers where the cylinders meet the case to get all that fuel/air mix in. If you go above +4mm on the crank you will need to trench the cases as well. The YPVS case is not a thick as a banshee case, so +7mm seems to be it's max, whereas it is said that the banshee will take machining for +10mm cranks. Of course you can weld up and otherwise modify the OEM cases, but aftermarket billet banshee cases are available for really big crank throws. FYI OEM Banshee cases are still available new from Yamaha at the time of writing.



Q. How much will this big cc engine really cost me?

A. How long is a piece of string? Depending on your setup you can spend anywhere from US$2k - 10k+.



Q. I just saw a cheapo (insert random cc size) mega kit on ebay, what do you think?

A. Sure, knock yourself out... I wouldn't but it's your money. Due diligence will always pay off with work like this. Speak to the supplier and read up on the forums before you spend your money, not after... And please don't email me about it asking my ‘advice’... All my knowledge and the best help I can hope to give you is condensed into these web pages. Read here, read forums and suppliers websites. Learn everything you can, then buy. Doing it the other way round will cost you more money and much more time in the long run, you can trust me an all those who went before you on that!



Q. How about I buy a bargain Athena kit from one supplier and then other parts from other places and maybe at different times?

A. Of course you can, but if you do that and then stroke the crank then you should know that the Athena supplied pistons will be no good to you, hence why lots of guys like the kits as they have everything ready to go. Buying a slightly cheaper Athena kit from ebay and throwing away pistons isn't really a great economy. You might think you will sell the old pistons, but there isn’t much of a market for Athena’s not-that-hot 68mm pistons so selling on doesn’t really work either. Plus, you will get more aftersales help from a single supplier as they should back their product, if you build a motor with other parts than they have tried and tested then a single supplier may not have the knowledge to help you fix a problem or advise on fitment, they might want to help more, but just can’t.



Q. The supplier site / ebay listing I just read said it will make 100bhp on 97RON pump fuel!!!!

A. Ohh nice...! But... Well... An upside is that just like how many liters go into a gallon, the USA fuel ‘RON’ ratings are not same as the ROW. In fact they are lower octane than many of us get at our pumps elsewhere, so you might get more power, who knows. And.... Remember jetting is depending on elevation as well, so beware of jetting out of the box if you live up a mountain. Bt the real nub of the issues is that of course nothing is more variable than different Dyno results of the same engine... take most dyno results with a pinch of salt unless a comparison was done on the same dyno, the same day, without changing any settings.



Q. How big can I really go?

A. 600+cc is possible from our parallel twins...



Q. Hold on, you make it sound like I can do something else... Can I build a triple?

A. Yes, billet cases are available for triples at around US$2k. You will need a new crank and 3 cylinders, 3 carbs and the space in your frame to mount it all in... Would be a fun project though, email me if you are building one, I’d love to know more.



Q. Can I supercharge or turbo charge these engines?

A. Well the short answer is 'yes'. But while you can do that it's not a common occurrence outside the banshee drag racers or salt flat speed kings. From what I've read a Turbo is the more obvious setup on a two stroke, supercharging is much more expensive and less helpful to the way a 2 stroke engine works due to pushing the fuel straight though the motor. Again email if you're doing one, I would love to know more.



Q. This all sounds great, I will ring a few suppliers and buy one then!

A. Cool, and do join a forum (click this text to see the friends pages here on this site for links) and show people what you are up to. When talking to the supplier remember that anyone who doesn't know road bikes, just wants to sell you the kit as it stands in its box, or just wants to build you a sand drag racer quad is not going to be an ideal partner for a road bike project.



Q. How can I get more info?

A. Join and read the forums... For the most about this kind of project you should check out the RDLCCRAZY and RZRD500 forums using the link above, that's where most of the info is for these engines in bikes, but the banshee forums are also full of good info as well of course.



Q. So all this said, you seem to favour the Athena kit?

A. Really the Athena 421 is what most people build as it works, but also it's well known on the forums as a good road solution, and its not *that* expensive. There are others other there and there is plenty more power to be had. From non-PV 68mm cylinders to all manner of mean monsters.... and since you can also stroke to +7 or +10 with case trenching you can build all sorts of sizes. E.g. a ported 443cc Athena should get you around 100bhp. But, bear in mind, Athena and 421 is the start point and banshee owners were there a long time back, that is a budget build for them, they go bigger and badder (600+) and chuck upwards of 10k in their motors for racing... you can even go for a triple with billet cases and then build up the cylinders in whatever size you can dream of on that... Potentially 900cc+! But it depends on what you want to spend.... that's the kicker, you must know what you want before you start. I was one of the first to document a 421 Athena LC on the forums and others have done them since and have theirs on the road, I've dragged my heels with other projects but since we have so many documented ones done now its a well known setup and it works for a fun bike. Sure you can go it alone with the some random 467.8cc kit off ebay, but I fear that won't be a quick build... You will be 'making it work in a bike' and having to find parts that fit like carb tops, an ignition, air filters, pipes that work and a curve etc. That stuff eats time up! If that's what you're happy to do, then I'm all ears and eyes to read about it as you tell us what you find, I might even build one in my next build if its a rocket ship, but if you want quick power with all new parts then doing something few (no one?) has done isn’t the path I'd say... just my 2c.



Q. Don’t want to be rude, but what did this cost you then?

A. Check out this thought on costs at the bottom of this page: My Yamaha RD Athena 421cc

.. And finally...



I can't state this enough... I really, really (yes REALLY!) do urge you to read up and talk to as many people who have done this type of thing as you can before you jump into buying these parts to be sure you know what you're getting into. You need to know some things about what you want to have at the end, that will answer the questions for the supplier about the domes sizes they need to cut etc. I wouldn't buy any cylinder kit blind without asking about the sort of engines the supplier has sold, and bear in mind that not all Athena cylinders are clean enough to be usable out of the box and bigger cylinders often can eat rings... food for thought... So, find out what is what, then make your choices and spend your heard earned money and then share the build so we can all hear the roar of your motor!



Above all, have fun.... and... go big or go home!
 
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Thanks.

I think he read through this. It was more specific questions like the power differences between the Serval and Cub for street, who can make a custom set of pipes, etc.
 
good course to seek info and plan first
I went nuts one winter several years ago on an RD350 a/c
ported, reeds, chambers, jetting
come spring it ran like a POS and never did get it sorted

this was pre-internet so it all word of mouth
so unless there is a proven set of mods that work together
one at time and tune in between is prolly the best course for these things

and on a YPVS bike, chances of messing it up would be incrementally larger
 
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Thanks.

I think he read through this. It was more specific questions like the power differences between the Serval and Cub for street, who can make a custom set of pipes, etc.

More CCs usually means more power.
Going past a 4mm stroker means you have to trench the cases or use one off billets cases. (Just because you are asking these questions means this is beyond your scope).
TSA and KillerATV are the only ones making pipes specifically for stroked RZ bikes.
Roger from Wicked is approachable to make specific changes to his pipes. He takes FOREVER.
TSA pipes were designed by Glyn of GPL Racing. He can be found in 2t forums by the name of "slinger". You may be able to convince him to make you some one off pipes, but he is pretty busy doing R&D.
You can use Swarbrick or TDR pipes designed for a TZ350. Both have a larger downtube, 41mm vs 38mm, than the street based pipes from TSA or Killer.
For truly custom pipes look in the snowmobile industry. Try Greg at Jaws Performance https://jawsperformance.com/
Are you looking for someone to make a set of custom pipes or design a set of custom pipes.
 
Does anyone know if he still logs in here?

I have a friend building a stroker 421 RZ350 and he wanted to ask him some questions. I sent him a PM before Christmas but no response yet.

TIA

Sorry. I don't log in a lot any more. I actually wanted to see how Omar was doing. Glad to see he has a new bike. He is very inspirational.

Sent you a PM. Happy to answer any questions. I just completed a new 443 myself

I'll keep checking back though.
 
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