FRZ 400 Mechanic | Page 2 | GTAMotorcycle.com

FRZ 400 Mechanic

my 600 motor is supposed to bolt right in. Would be tempted if I find an FZR 400 in great condition and a blown motor. Post pics of yours?
 
Don't condemn the engine before you do some diagnostics. Set the valve clearances, check compression, replace the spark plugs, and go into the carbs and install one size bigger pilot jets (available from a good Mikuni dealer e.g. Winners Circle in Markham).

These engines are getting quite hard to find in good order. Anything you find could very well have its own problems (there's a reason why it's being sold). "Reconditioned" means about $700 just in parts to do it properly (all new gaskets, piston rings if you can find them, deglaze cylinders, all new main and rod bearings, and fix the assembled-in flaw with the oil restrictor jets at two of the crank journals) and that's if it doesn't have other problems. A cheap used engine for a few hundred bucks needs to be disassembled and gone through ... see above.

Further note on something I touched on above. Yamaha built every single one of these engines with a mistake inside it. At the center main journal on each side (group of 3 left, group of 3 right) that journal is the one that does not supply a con-rod bearing, so there is a screwed-in restrictor jet in the oil supply to it. Their thinking was probably that the journal is covering it, so the jet can't escape, so they just screwed it in a few turns and left it loose in there. Problem is, when it unscrews, it goes loose in the threads and allows extra oil to bypass which in turn starves one of the rod bearings. I always take these jets out, put a tiny drop of loctite on the threads, then screw them all the way in until they are bottomed in the threads. Takes 2 minutes. Getting to those jets ... requires splitting the crankcases. Splitting the crankcases ... requires disassembling the top end because there are two crankcase bolts that you can't get to without removing the cylinder block. That means new rings and new gaskets.

See my overhaul thread linked to earlier in this thread.
 
Also, a YZF engine will bolt in if you swap oil pans. (The YZF oil pan won't clear the FZR suspension linkage, but it's otherwise a straight swap.) You will need to do something about the ECU (the rev limit is different ... a 400 rev limit will blow a 600 engine and the wiring requires modification to swap ECUs and make this work) and the cooling fan won't fit, and you will not be able to use the airbox. But it's been done many times.
 
fugue said:
Hard start is indeed a symptom of tight valves, but there could be other reasons, too.
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Compression test will be low if valves are off.
 
I don’t have many pics and the bike is apart now so I’ll take some more later. Here is the only one I have on my phone.

D7CED191-5C71-4434-B427-81467626C934.jpeg
 
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I wouldn't even be thinking about an engine swap until you know what you have.
You bought the bike at 35k, it now has 75k without a valve check. Do one.
Do any other maintenance that is due and I think you'll be surprised.

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Exactly, new battery, new fluids and filters, check the wiring for faults, carefully check valve clearances and put in a fresh gasket then clean and sync the carbs and put in new spark plugs. Might be wroth checking the clutch too if you haven't done that since you bought it.

Looks clean, you should keep it original or period correct for as long as possible. Unless you want to sell it to me.
 
Compression and leakdown willl tell you everything you need to know. If it runs fine but just has trouble starting, it’s probably something small and easy. All you need is air, spark, and compression for it to fire.
 
Did a compression test today and only one cylinder was good. Next check is the valve clearance and then we will see what comes next. Thanks again to everyone for the help!
 
What were the numbers and how far off spec were they? Leakdown will point you towards valves, rings or coolant gasket.
 
The best one was 110 psi, all of the rest were under 30. Needless to say it looks like the head and maybe the engine will need some work. Checking the valve clearance next.

I’d like to see if I can fix the bike as I always planned to keep it forever for casual weekend riding. I’d think about getting another bike but don’t have anywhere to keep it right now.
 
nigel said:
The best one was 110 psi, all of the rest were under 30. Needless to say it looks like the head and maybe the engine will need some work. Checking the valve clearance next.

I’d like to see if I can fix the bike as I always planned to keep it forever for casual weekend riding. I’d think about getting another bike but don’t have anywhere to keep it right now.
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Under 30? That's pretty extreme. Not being rude, but are you sure you did the test correctly?

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Pull the valve adjuster cover, roll the engine around until it reaches TDC on each cylinder and check your valve clearances. Is almost too easy, if valves don't open and close when they should your compression will suk. If you did have a hole in a piston, bent valves or busted rings your compression would be near zero and there would be all sorts of other symptoms like engine oil appearing in places it shouldn't be.

... this is where you are going to wish it was a single cylinder engine or a BMW boxer twin.
 
We were surprised how low the compression was as well. The throttle was wide open and we double checked all of them. Going to check the clearance next. The engine did run with no obvious problems when we had it running.
 
Do the valves have hydraulic lifters? Could it be that since it sat for three years they need priming of some sort?
 
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