RZ350 Stroker Motor

OK. I'm building a RD350LC Hybrid and I figure I might as well spend my money before Trudeau does so I was thinking about building a stroker for it. The crank needs rebuilt anyway so it would be a good time to do it.

I've already installed the VJ22 front and rear ends and the frame has had significant strengthening.

Who's done it? Pros, Cons, Pointers? Any help would be most appreciated.

Thanks in advance

I have 3.

I have a 385 which is a +4MM with the standard RZ barrels and retains the PowerValves but has a very aggressive port

I have a 421 which is a +4 crank with the Athena 68MM big bore kit

And I also have a 443 build from 68MM Serval Cub block with a +7MM crank.


You don't say what kind of riding you will be doing - Track, Street, etc. Its hard to advise as all of these motors feel completely different. For the street I prefer the Serval setup. For trackdays I prefer the Standard YPVS barrels with the porting.

One thing I will say is that the following are generalities that I have learned by trial and error.

The Serval is the best engineered block and produces more power and torque lower in the rev range so is a better block for the street.

Make sure you go with the long rod set up, i.e. 115MM the 110mm rod angle is too much and pushes the piston into the barrel causing more wear.

For the 115mm rods you will need 795 series Wiseco's (or equivalent) that offset the small end by 5mm. The challenge is that they are only available on 0.5mm increments so you need to jump 2 piston sizes during a re-bore.

Even with all that the piston still runs out of the cylinder by a couple of millimetres. You can either put a plate under the barrel to raise the cylinder, or you can cut the head to allow the piston to travel into it. Many people have tried the plate and found it wanting as it completely goofs up the port timing. Milling the head or buying a NOSS or Wicked head with the appropriate domes is a better way to go.

There are 2 many variables to reply but if you let me know what type of riding you want to do I can definitely help out. If you are local we can meet up for a coffee. Carbs, Pipes and Timing also make a huge difference but its hard to advise without knowing more.

Great info Delboy!
The fact that you have not 1 but three of these in different variants is amazing!

I've started gathering parts for a 385 with +4mm with standard RZ barrels with mild port, 34mm carbs and GPL stroker pipes.
Not sure what air box yet.
Looking for a motor that will do both street and some trackdays.
I still haven't ruled out the Athena kit.

Are you still running the oil pump on your 385?

Which exahusts, carbs and airbox are you running with each configuration?

If you want to beat on your Yamaha twin I suggest you go the long rod route no matter what.
If you go more than 4mm stroke you'll have to trench the cases.
Toss the pump, it's just one more thing to go wrong.
Unless you plan on running CV carbs, (that would be a mistake) don't run any airbox, just foam filters. If you want to get trick, put an extension on the carb bell before the filter.
As Dellboy said, the best "all round" motor is a done Ypvs setup. Most of the aftermarket stuff is for peak HP and aren't much fun on the street. I have a WickedATV 421 RZ that is STUPID fast, but impossible to keep on the pipe on the street.
If you already have the pipes, Glen makes GREAT pipes, I would build a motor that the pipes will work with. I usually build a motor THEN get/build a pipe that will work with that motor. The dimensions of the pipe sort of dictate the dimensions of the motor.
Spend your moneys on the head. Get the squish right, AND GET IT PINNED. The LC head was designed right about the time when we went from leaded to un-leaded fuel and they didn't have the combustion chamber figured out yet. The LC has a smooth dome for a combustion chamber and un-leaded fuel wants a "top-hat" combustion chamber. Since you're going to be getting the head machined anyway....
... and you're going to need a bigger rad and toss the thermostat
... use a YZ250 clutch and get an aftermarket billet basket that holds 7 plates (from a Banshee) BUT DO NOT use the Barnett springs (They're too long and you have to modify EVERYTHING or they stack
... use YZ or Mototassinari reed block and stuff the reed cage (Make the reed chamber the smallest volume possible).
... if you going to run VM34 carbs (The TMX or PKs are better) have the venturi of the carb counter bored to the same diameter as the slide (it will flow much better).

That's all I got off the top of my head. Keep us informed, there is tons of info about these motors. I have been racing them since they were new. The oldest I have is a '72 R5, the newest is an '89 Lietner and Bush RZ Cup bike.

gammaguy21 said:

Great info Delboy!
The fact that you have not 1 but three of these in different variants is amazing!

I've started gathering parts for a 385 with +4mm with standard RZ barrels with mild port, 34mm carbs and GPL stroker pipes.
Not sure what air box yet.
Looking for a motor that will do both street and some trackdays.
I still haven't ruled out the Athena kit.

Are you still running the oil pump on your 385?

Which exahusts, carbs and airbox are you running with each configuration?

Click to expand...

Yes, it’s those long cold Canadian winters. Have to have something to do.

On the 385 I'm running Glyn's pipes. You will be very happy with them. They are great. The porting was done by Mick Abbey to Glyn's spec and Vance at Oshawa Precision machined the original head. I'm running PWK 33's on that one, foam filters and a combo Zeeltronic that has the CDI and YPVS controller build into one unit

For the 421, I’ve got Kenny’s (TSA) pipes that I bought second hand and am running the Athena barrels and heads with Domes from Roger over at Wicked ATV. It has PWK35’s and foam filters and the Zeeltronic CDI being fed by a RD350LC generator. BTW. Glyn's pipes will also work great on this motor

The 443 was a kit I had on an old banshee. It’s the CPI Serval block that they describe as a “Dune port” for playing around. It probably makes it peak power by 8500 rpm but just pulls like a train from about 4 to 8.5, its like a four stroke. It’s very linear and has a lot of torque. It’s really good for the street, probably not so good from the track. That one has a NOSS head and PWK 39’s. It has Matt Shearer pipes that I modified to fit the RZ frame. It also has a RD350LC generator. I bought the barrels, head and crank as a kit from Farm and Sand Toys Racing. Jeff is one of the cheapest around

For them all I had to run Rogers billet intakes to lift the bigger carbs above the clutch arm. That leads to some issues with the cable routing as they have to go over the frame rail where the rectifier bracket clips on, so you need to get rid of that. I just made a smaller plate from Aluminium that the rectifier and the Zeel get bolted to on opposite sides. If that makes sense

All of them are running either Vforce 3 or 4 reeds.

For the Athena and NOSS head, I used and inline KTM thermostat on the hose between the head and radiator. If its track only you probably don't need it but I found that spring and fall on the street the temperature would drop right into the cold region of the gauge.

All the cranks are +4 or +7 with the 115 rods. One of them came from TSS and it’s a nice piece of kit but unfortunately they are gone. The +7 is Hotrods that was rebuild by Willie in Ajax using genuine Yamaha big ends which seems to be their weakest spot, although everyone raves about their rods. I know Roger ate Wicket and Jeff at FAST install a lot of Hotrods Rods

I’m currently running them all without the pump, but am going to send a couple of pumps to Arrow over the winter, He can rebuild them with more capacity for the stroker motors. I’ll probably put the pumps back on the 421 and 443.

For some road and some track you’re probably best off with the RZ barrels or the Athena. The Serval is really nice for the street but will not rev high.

BTW, Matt can do pipes that bolt up directly to the RZ. I happened to have the set from the banshee that I cut and re-welded to fit the frame as I'm cheap

Thanks. Exactly what I was looking for. PM sent.

BTW. The other nice thing I found is that since they are too old for most insurance companies I have to go to a broker that specializes in vintage insurance. They really don't seem to care/understand/worry about all the mods even though I declare them (with Dalton Timmis I also have the bike inspected and appraised) insurance is still very cheap within their restrictions. They seem to be more worried about travelling less that 3000km per year and things like that.

Thanks for the info bitzz/ Delboy!

Looks like that's two votes for the long rod. Good thing, I was initially thinking the 110mm rods.
I didn't want to trench the cases so the plan was to go for the +4mm.

This bike with the stroker motor is from all the bits and pieces I've collected over the years as spares, without much thought to putting something together. I wanted something slightly different from the rz motor I'm running now, so I bought up stuff cheap when they came up... that's how I ended up with Glyn's stroker pipes. I was half hoping Glyn would get back in the game so that I could have him set up the motor for his pipes. If not, then I'm hoping I can get him to give me the specs for the porting or I guess I could send the barrels to Mick Abbey. Good to know that Glyn's pipes could also work on the Athena kit, as I may end up going that way. Actually, I don't even know if his pipes will fit the chassis I have... as this is really an afterthought bike.

I have a unknown billet banshee carb intake for lager carbs... but this isn't going in an rz chasis, so I'm not sure what to expect with the cable routing. Good to know that I may need to trouble shoot that in the future.

I'm also considering Arrow for an oil pump. Seems like he gets a lot of good reviews.

Delboy, good to know that the TSS crank worked out for you... seems there was alot bad stuff that came from that.
Luckily, I got my rs250/rz engine cradle from yamagamma out of BC, way before TSS started, as he was the one who developed it as a kit. Thanks for the insurance info too!

bitzz, sorry, I'm not sure I get what you mean by "AND GET IT PINNED"?

Seems like there's some extensive rz/rd knowledge on here that I wasn't really expecting. Glad this thread has come up.:thumbup:

I don't log in here a lot but this is very interesting

I have a RZ rolling chassis and bottom end in the garage. I sold the jugs and head many years ago. It has a solid tank and body work

I put it on Kijiji in the summer but got a number of offers for $200 or $300 or trade for a 1984 snowmoblie that needs work or a wet saw for tiles. LOL

This has given me a little push to try and get it on the road again.

I like the Serval option as it will only be for the street. Can I ask you a question. Is it possible to use the Serval with the +4 mm crank? I don't want to go to the bother of trenching the cases.

Cheers, Steve

gammaguy21 said:

Thanks for the info bitzz/ Delboy!

Looks like that's two votes for the long rod. Good thing, I was initially thinking the 110mm rods.
I didn't want to trench the cases so the plan was to go for the +4mm.

This bike with the stroker motor is from all the bits and pieces I've collected over the years as spares, without much thought to putting something together. I wanted something slightly different from the rz motor I'm running now, so I bought up stuff cheap when they came up... that's how I ended up with Glyn's stroker pipes. I was half hoping Glyn would get back in the game so that I could have him set up the motor for his pipes. If not, then I'm hoping I can get him to give me the specs for the porting or I guess I could send the barrels to Mick Abbey. Good to know that Glyn's pipes could also work on the Athena kit, as I may end up going that way. Actually, I don't even know if his pipes will fit the chassis I have... as this is really an afterthought bike.

I have a unknown billet banshee carb intake for lager carbs... but this isn't going in an rz chasis, so I'm not sure what to expect with the cable routing. Good to know that I may need to trouble shoot that in the future.

I'm also considering Arrow for an oil pump. Seems like he gets a lot of good reviews.

Delboy, good to know that the TSS crank worked out for you... seems there was alot bad stuff that came from that.
Luckily, I got my rs250/rz engine cradle from yamagamma out of BC, way before TSS started, as he was the one who developed it as a kit. Thanks for the insurance info too!

bitzz, sorry, I'm not sure I get what you mean by "AND GET IT PINNED"?

Seems like there's some extensive rz/rd knowledge on here that I wasn't really expecting. Glad this thread has come up.:thumbup:

Click to expand...

I think the original TSS cranks were really good and they used high quality components. When they started messing around with that 90 degree offset crank everything went pear shaped. They just could never get it to work

Ulsterman said:

I don't log in here a lot but this is very interesting

I have a RZ rolling chassis and bottom end in the garage. I sold the jugs and head many years ago. It has a solid tank and body work

I put it on Kijiji in the summer but got a number of offers for $200 or $300 or trade for a 1984 snowmoblie that needs work or a wet saw for tiles. LOL

This has given me a little push to try and get it on the road again.

I like the Serval option as it will only be for the street. Can I ask you a question. Is it possible to use the Serval with the +4 mm crank? I don't want to go to the bother of trenching the cases.

Cheers, Steve

Click to expand...

Steve. Yes, it will work with the +4. I think its the lower porting that gives it that nice power band. Mine is +7 as i has a +7 crank in the doner Banshee

Thanks Delboy and Bitzz. You have made an old man very happy.

Just looked at the pricing for parts and it high but doable, I figure I have to take the figure I came up with and double it, but at least its something unique and a little different from the R3's and the 300 Ninja. I'm also a 2 stroke guy at heart and it wouldn't be a daily driver

I'll pull it out at the weekend and make a start. No doubt I'll be back with some really dumb questions.

Would either of you to mind PMing me your email addy. I don't come on here a lot and it would be easier if I needed to ask questons.

Cheers, Steve

^^^ PM Sent

The Yamaha head bolt setup blows chunks. After you do all that good machine work to the head, to very small tolerances, the loose setup of head bolts will allow you to put the head on off center by as much as 0.040.
"Pinning" the head means you use a locating dowel installed in the head or barrel to locate the head precisely.

Just so you all know; You will always increase torque by increasing the stroke. Torque is a function of stroke.

There was a lot more to the demise of TSS than that 90 degree crank. It was mostly that Steve liked to mouth off about stuff he really didn't know about (Steve was not the driving force behind TSS, he was the front man). The melt down is archived at USA2strokes... it was a lot of interweb fun.

If you want to play with Yamaha 2Ts
http://www.rzrd500.com/phpBB3/
http://www.2strokeworld.com/forum/index.php

If you have question, dumb or not, ask them here so everyone can profit from them.

One more question.

Are the Indian tanks on Ebay any good? I have some pinholes and am having a hard time finding something better.

j2 said:

One more question.

Are the Indian tanks on Ebay any good? I have some pinholes and am having a hard time finding something better.

Click to expand...

In a word.... No

I have never read a good review. A guy in the CVMG bought one and it was very rough, its wasn't symmetrical and it leaked. The tank you have is probably better and it can be repaired. Its not that difficult

I just did one for a guy up in Port Severn who is building a bike for the VRRA. They have a few low points where the water lies where they rust really badly. I just cut that out and weld or preferable braze in new metal. I then get it pressure tested at a rad shop and I personally put a liner in it, some people don't like them. I've been using KBS Gold lately.

Its $10 to have it boiled out at the rad shop and about 20-30 bucks in materials + paint. If you buy an ebay tank you have to paint it anyway

I'll post some before and after pics of his tank tonight. Its still hanging in my little booth.

But you're tank can be repaired.

BTW, Don't weld without having it boiled out

bitzz said:

The Yamaha head bolt setup blows chunks. After you do all that good machine work to the head, to very small tolerances, the loose setup of head bolts will allow you to put the head on off center by as much as 0.040.
"Pinning" the head means you use a locating dowel installed in the head or barrel to locate the head precisely.

Just so you all know; You will always increase torque by increasing the stroke. Torque is a function of stroke.

There was a lot more to the demise of TSS than that 90 degree crank. It was mostly that Steve liked to mouth off about stuff he really didn't know about (Steve was not the driving force behind TSS, he was the front man). The melt down is archived at USA2strokes... it was a lot of interweb fun.

If you want to play with Yamaha 2Ts
http://www.rzrd500.com/phpBB3/
http://www.2strokeworld.com/forum/index.php

If you have question, dumb or not, ask them here so everyone can profit from them.

Click to expand...

Yup. I drunk the 90 degree coolaid I had one. I still have it. I'm going to take it to Willie and have him rebuild it as a 180. The vibration or harmonics or what ever you want to call it between 5 and 7 was insane. It was so bad it used to froth the fuel in the bowls leading to misfires

I cant comment on the HR issues. Both had very different expectations. That got a little nasty and it was all aired in public

So this is normally where these tanks go. This one is a RZ but the RD ones rot in the same places

The bottom outside at the low points. Any water in the fuel just lies there. You can see its also rotten right underneath between the edge and the seam. BTW, it looks like house paint on it



And on the inside



Don't use bondo to cover rust




Metal cut out and replaced. The hard bit is recreating the right shape. I had to do this with three pieces, You can still see a little tiny ridge on the seam but that will be covered by the side panel



Same for the inside. New lug installed as well





Front pulled out and fixed.



The fuel filler still had the masking tape on it and I haven't wet sanded and buffed yet so its not mirror smooth but you get the idea. I wanted to post this just to show you that even a tank that looks really far gone can have years of service left in it. Do not throw it out

BTW, this tank was advertised on Kijiji as "good condition, just needs liner"

bitzz said:

The Yamaha head bolt setup blows chunks. After you do all that good machine work to the head, to very small tolerances, the loose setup of head bolts will allow you to put the head on off center by as much as 0.040.
"Pinning" the head means you use a locating dowel installed in the head or barrel to locate the head precisely.

Just so you all know; You will always increase torque by increasing the stroke. Torque is a function of stroke.

There was a lot more to the demise of TSS than that 90 degree crank. It was mostly that Steve liked to mouth off about stuff he really didn't know about (Steve was not the driving force behind TSS, he was the front man). The melt down is archived at USA2strokes... it was a lot of interweb fun.

If you want to play with Yamaha 2Ts
http://www.rzrd500.com/phpBB3/
http://www.2strokeworld.com/forum/index.php

Click to expand...

Thanks bitzz for the "Pinning" explanation. I've only rebuilt a couple of motors and didn't realize there was so much slop in the rz head.

I'm already a member of both of those forums... but there aren't a lot of members that have had or worked on this many variants of the stroker engine and are willing to give good comparison info. Lots of good info on both those forums for sure.

The public airing of the TSS downfall was very ugly, a bunch of people lost lots of money, but it definitely was entertaining.

Delboy, nice job restoring that tank.

Delboy said:

In a word.... No

I have never read a good review. A guy in the CVMG bought one and it was very rough, its wasn't symmetrical and it leaked. The tank you have is probably better and it can be repaired. Its not that difficult

I just did one for a guy up in Port Severn who is building a bike for the VRRA. They have a few low points where the water lies where they rust really badly. I just cut that out and weld or preferable braze in new metal. I then get it pressure tested at a rad shop and I personally put a liner in it, some people don't like them. I've been using KBS Gold lately.

Its $10 to have it boiled out at the rad shop and about 20-30 bucks in materials + paint. If you buy an ebay tank you have to paint it anyway

I'll post some before and after pics of his tank tonight. Its still hanging in my little booth.

But you're tank can be repaired.

BTW, Don't weld without having it boiled out

Click to expand...

I hate to ask but do you think it would be possible to take a look at mine?