FZR400 winter overhaul | Page 5 | GTAMotorcycle.com

FZR400 winter overhaul

Brian P

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Me and carburetors have a love/hate relationship. Love because there's a lot less wiring and computers involved. Hate because they can be finicky beasts ... and they are being finicky!

Filled cooling system (just with water for now), put a bit of fuel in the tank (and I just filled up my snowblower from the same jerry can yesterday, and it works), hooked up battery ground. Switched on the key - we have electrical. Hit the starter button - lots of cranking but no fire. Not a hint of firing. From the sound of the engine while cranking, compression sounds even across all four (although on initial startup with new rings, no question the compression is going to be lower than it will eventually end up).

Pulled a spark plug cap, inserted an old spark plug and arranged to ground it against the frame, crank - strong spark. Not an ignition problem.

Tried spraying WD40 directly into each velocity stack while cranking - no dice.

Took a propane torch and fed propane directly into the airbox (with the cover removed) for several seconds then tried cranking. Propane has the advantage that if you misjudge and use too much, it won't foul the spark plugs with fuel. It fired a couple of times. Tried again. It fired enough to rev up to probably 4000 rpm then quit.

It ran long enough to reveal that I have an exhaust leak at the cylinder head - that's what I get for trying to re-use exhaust gaskets. This wouldn't affect firing during cranking but it could affect whether the engine will want to keep running once it fires. I'll have to fix that, then try again.
 

FiReSTaRT

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Fingers crossed!
 

skip

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Subscribed just because I miss tinkering with my FZR400
 

mxs

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Man, you are not the only one who has love hate relationship with carbs. I had those things out on my bike probably more often then you ....

So, you have a fuel feed issue ... have you fixed that yet? Don't slack now pls ... LOL ... you are almost there.
 

Brian P

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Fixed the exhaust leak. And, we have a runner. Turns out the reason it wasn't starting is that something's holding the throttles open slightly and/or letting in unmetered air. When it did start (with the exhaust leak fixed and a bit of propane fed into the airbox!) it immediately took off for 10,000 rpm. Wasn't what I had in mind for a break-in. I suspect the carbs are not properly seated in the intake ducts thus causing a vacuum leak - because of the way the carbs are oriented, it's impossible to see the front of them when setting them down on the engine.
 

Brian P

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Well, I'm happy. One more project taken care of on the chassis. Bye-bye, crappy FZR stock voltage regulator. This is a current-technology MOSFET regulator similar to that used on most newer bikes. I bought a kit with the required plugs for the harness, cut off the old plugs (the old regulator had melted the stock connector the last time it fried, anyhow), soldered in extensions for the wiring, and hooked it up so it plugs in just like an OEM regulator on a newer bike. I'm going to have to trim the top cooling fin so that it doesn't interfere with the bodywork, but this one has enough fins so that it shouldn't be an issue.



Still waiting for the extra washer under the countershaft nut (just got the phone call saying that it's in) so I still need to hook up the clutch.



And, obviously the rear wheel is not installed. I ended up placing the order for the budget-blowing brand new Penske rear shock built to spec, because a new seal for the WP shock has proved unobtainable. The stock shock that's in the bike now is only good for wheeling the bike around in the shop, and the rear wheel has to come out to change the shock anyhow, so no point putting the rear wheel on. Shock should arrive sometime in January.



But ... I'm happy. Upon investigating how the carbs were sitting on the intake boots, I found and fixed a little alignment problem. With no more air leak, it started up with a momentary touch of the starter button, and idles smoothly and quietly. It sounds like a new engine (and for practical purposes, it almost is). Charging voltage is good, so the new regulator works. I ran the engine long enough with the fuel pump unplugged to empty out the carbs, also serving as the first heat cycle on the fresh piston rings, and called it DONE!
 

Brian P

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Inspiration for phase 2 of this project ... Rich Oliver's 1990 TZ250 AMA bike on display at the Barber museum, which is period correct since the FZR under discussion also happens to be a 1990 model.



What looks red in the photo is actually fluorescent reddish-orange, which doesn't photograph well. I took my own photo of this bike at the Barber museum, and it was even further off. The white is a pearl white that Yamaha commonly used in that era.
 

Brian P

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Parts have been dropped off at Reflections Auto Refinishing (a.k.a. carboncat) with instructions to make ^that happen :)
 

JohnnyP636

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Parts have been dropped off at Reflections Auto Refinishing (a.k.a. carboncat) with instructions to make ^that happen :)
Question for you FZR 400 gurus, I have a customer here with an 88, 2 of his carb diaphragms are ripped...Yamaha has them discontinued....So any idea for a source for good used ones? Or even an aftermarket reproduction?

Thanks for any info
 

WoBblyCaT

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Inspiration for phase 2 of this project ... Rich Oliver's 1990 TZ250 AMA bike on display at the Barber museum, which is period correct since the FZR under discussion also happens to be a 1990 model.



What looks red in the photo is actually fluorescent reddish-orange, which doesn't photograph well. I took my own photo of this bike at the Barber museum, and it was even further off. The white is a pearl white that Yamaha commonly used in that era.
Are you going to wear period correct leathers:



Or period correct high waisted bikini?
 

1978550

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Great Thread dedication Brian! Its like reading a shop manual as I read your thread. Clear, concise and I feel like you really know what your talking about. Great job on the bike too. I love the attention to detail and care you put in. Cant wait to see the painted parts.
 

Brian P

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Question for you FZR 400 gurus, I have a customer here with an 88, 2 of his carb diaphragms are ripped...Yamaha has them discontinued....So any idea for a source for good used ones? Or even an aftermarket reproduction?

Thanks for any info
The carbs are Mikuni BDS 32. It's pretty likely that the diaphragm is the same piece as on some other bike that uses the same basic carb model, or at least close enough to be interchangeable.

From a bit of poking around, it looks like the Mikuni BS 32 is more common. ("D" = downdraft = Yamaha FZR layout, the side-draft was the old "universal japanese motorcycle" layout.) The diaphragm is different but it's probably close enough that a bit of ingenuity could make it work. The diff is that the BDS diaphragm has that little hole for the choke passage which goes through the diaphragm, and the BS doesn't appear to.
 

Brian P

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Finally an update. Shock came in. Penske includes a shock dyno and a complete tuning and rebuild manual. Nice.



Comparison of old shock to new shock revealed a couple of things.

The width of the eye across the top was just a hair smaller ... I made up a little spacer to take up the gap.

On the old shock, the bottom bolt threaded into one side of the clevis. On the new one, it's a through hole meant to be used with a nut (similar to stock), which I don't have. That didn't stop putting it in place.



One of the first photos showed where I wanted to put the shock's remote reservoir. Done!



Another difference between the old shock and this one, is that this one is about 5mm longer, even when set on the lowest ride height setting (the old one didn't have adjustable ride height). It will probably want less preload (i.e. more rider-aboard sag) to maintain the correct steering geometry. In general, I don't mind that. These bikes normally want a lot of preload to get the geometry right, resulting in no static sag (it only gets sag with rider on board). For now, I just installed the shock as it came. There's enough differences in spring rates front and rear that it's going to need a complete set-up once it's possible to ride it.

I am anticipating another update next week ...
 

kirbster

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I have a spare set of carbs.... PM me and we can work something out.

Question for you FZR 400 gurus, I have a customer here with an 88, 2 of his carb diaphragms are ripped...Yamaha has them discontinued....So any idea for a source for good used ones? Or even an aftermarket reproduction?

Thanks for any info
 

GateKeeper

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Hey Brian....if I can ask, what does one of those shock go for ? I have put back the stock shock on my FZ for now, but an upgrade to a newer one would be a nice addition.

Thanks
 

Brian P

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Several different variations of that shock to choose from at different price levels, http://www.penskeshocks.com/ - and the prices on that website are MSRP; talk to your local shop to see what they can do. They're less pricey than Ohlins but definitely not cheap!
 

rye

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Did you get the fairings back from carboncat yet?? And I'm curious...what's he charging you? (you can PM me if you don't want to say it out here)

I got quoted $400 to do my fairings & tank at my local paint shop..and that was with me doing the prep work and wet sanding and polishing after, which I think is pretty high considering I'm doing a lot of the work.
 

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