FZR400 long term project

Hey y'all,

Quick bio: Engineering student, only dirtbike riding experience as of now, have rebuilt a chevy 350.

So a while back I picked up a bike from a buddy for $300, sight unseen.
It was sold to me as a 300, but turned out to be an 1989 FZR400.

I've done some reading up on the bike, as well as disassembling most of it.
The structural parts are in good condition, except for a quarter sized dent in the frame.
The bad news is the engine, the piston has rusted itself to the jug in cylinder 1, as well as a broken clutch boss.

I don't think its unfixable, but I'm in college and can't really afford those oversize pistons, as well as the machining labor.

So the plan right now is to make this a long term project, and pick up a running bike to learn on for like 1k until this is done.

I'm going to use this thread as an update log, as well as a way to get advice from anyone who wants to throw it my way.

Any ideas for swaps or upgrades are welcome, I've considered the 600 swap, but the idea of using an rz500 engine sounds fun as hell.

 

I have owned/rebuilt several FZR400s over the years. As you will discover they are special bikes. There are also several members of this forum that will agree! Check out this link here:
https://web.archive.org/web/2015110...fzr400/FZR400 Frequently Asked Questions.html
Feel free to throw out any questions and I look forward to your updates as you make progress. Also where are you located?

 

I was addicted to them for years. It's tough to break the habit, but there are groups for help. Seek one immediately before you give in completely. Next thing you know, you'll have a garage full of them. Nobody ever owns just one

 

Depending upon your Ditchdefinutiin if fun... the RZ 500 idea...the motor is a boat anchor...and you will spend approx 4-7 k just on the motor in addition to fabrication costs.
400s are a great bike, forget the "speed" and enjoy the lightweight and great handling...there's 100s of other bikes
out there that are fast

 

Ta- Dah!!!!!

1990 Yamaha FZR400 part out | 13x Forums

 

They are huge entertainment to row along on the gearbox, keeping it in the powerband (which was way high for the day). The only time I got pulled over in the last 40 years was on an FZR400.

An FZR600 comversion is probably cheaper/easier (since there are still so many of them around) than repairing or replacing the engine with another 400. The problem I had with the 600 was cooling: not enough room for the 600 rad and fan. A couple server size muffin fans might work tho'. I tried smaller PC fans, but no bueno (this was in Phoenix, however).

 

I have removed stuck pistons, cleaned, honed and just put back together. It all depends on how badly things are corroded.

If things clean up OK, just check the piston skirt to cylinder wall clearance with a feeler gauge. Before I had hones, I have cleaned up cylinders with just sand paper but it is time consuming.

I bring this up cause of the money thing. If the bike is just going to get occasional street use (no sustained red line like racing) you can get by with fairly large piston clearances.

If the above will not work, I bet you could find a used and usable 400 cylinder. You may only need to buy one used piston.

I'd try to stick with the 400 engine. The 600 would probably be the easiest possible swap but still not like falling of a log. If the budget is tight even the 600 swap may be non trivial since it's not just the engine but some accessories will be needed.

 

Currently living in Central Virginia, I appreciate the Wayback machine link, I've found some really good stuff using it.

 

I guess I'm not too opposed to trying to fix this engine, I'll probably soak the cylinder-piston combo in that marvel mystery oil stuff and see if it wants to come free.

Do you have any recommendations for the clearance I should look for? I know there's some general percentage recommendations, as well as those in the service manual.

 

Pictures man!...Pictures!

 

https://www.manualslib.com/manual/903971/Yamaha-Fzr400-1988-1989.html?page=170#manual

The above link appears to be from a Yamaha service manual on the bike. I would find similar dimensions in another place also but they do sound in line with my experience with other bikes.

When you use these max/min dimensions the limit is .0041 inch as an upper limit for piston to cylinder clearance. From looking at this information the new set up is around .002 inch.

If you really think you might do this, I'll share how to remove a stuck piston, how to hone with a minimum increase in bore, how to use a feeler gauge for piston clearance and the possible reuse of rings. That is if you need it.

 

I’d appreciate any advice you’d be willing to give me, I will say there are a couple other things I’m fairly sure are wrong with the engine. I’ll be getting some pictures of the engine on here in 2ish weeks, because it’s at school and I’m at home.

 

These are the two most zoomed out shots I had, I guess I never took a real full picture of the bike when it was together.

 

check your PM's

 

If I were you and wanted to actually get this going again, I'd buy the running motor (and whatever else you need) from Randy who is parting a 400 in that thread mentioned above if you can figure out shipping. You can't beat $400 for a running motor - you'll likely have that much in fixing yours with gaskets/rings/etc. I realize you're a broke college student, but you did ask for advice

 

I should clarify, it’s not that I’m completely broke, I’ve just been advised by friends that getting a bike is something called “a poor financial decision”, whatever that means

 

Stuck piston. On a multi obviously harder than a single. After taking off head, get the base gasket /jug free. Use penetrating oil. You'll get enough wiggle to see what pistons are free. If the stuck one is not at BDC you want to tap the piston. I use a large socket on the piston to spread out the load away from the center. Tap tap. You will also have to determine if any valve stems are stuck, especially if there were any open valves like probably at the piston that corroded. If stuff is really stuck you might separate the cases and remove the rod caps to get it apart.

Hone. Use a hone that flexes like a glaze breaker or just sand paper by hand to remove corrosion. Don't use a hone with long ridged stones. They can remove material quickly.

Piston clearance. After the cylinder looks good again, use a feeler gauge to check the piston skirt to cylinder wall. Look on YouTube but the gist is usable pistons are larger just above the bottom so that is where they are checked against the cylinder. Check in multiple places. The above mentioned reference I found showed .0041 max but verify that for yourself.

If the rings clean up nice, are not discolored and are OK on end gap it is probably OK to reuse them.

I agree with Billy. A good running motor for $400 is good.

 

That is such a cute thing to post on a racing forum.
Most of us that race have that as a statement to live by. Go ahead and spend the money on the bike and then make a bunch more "poor financial decisions." That is where the fun is and don't forget there are all kind of good meals to be had out of ramen and hotdogs.

 

Oh for sure everyone on here is making "poor financial decisions" with motorcycles. Two things I love on this:
Back in the day (yes I'm old) Sam Fleming of the Army of Darkness endurance team wrote articles in RRW (maybe he still does...) and for whatever reason they had to skip a race weekend. I thought it was one of the most true things ever written when he wrote something like "So since we couldn't go racing we all gathered in the driveway and lit a pile of hundred dollar bills on fire, to get the same effect".

Funny comment #2: A friend owns a motorcycle dealership and there was a couple in the shop looking at gear. My friend overhears the guy say something about liking a helmet or jacket or whatever and the lady says "Yes its nice but do you really need it?" My friend chimes in "Uhhh... this is a motorcycle shop. There's absolutely nothing in here that anyone NEEDS."

 

"a motorcycle is a poor financial decision; whatever that means"

If it wasn't for motorcycles I would have been able to finish college, I wouldn't have to worry about spending money on 80s 90s motorcycles.

You will always lose money on a motorcycle even if they go up in value eventually you may break even but doubtful...lol