fzr 750 seized motor

[dvsbob]

i was given a 1987 fzr750 by a mate(well so i thought). it wasn't running but i thoufght what the hell. this little "project" has now become a full on obsession. i will not rest until i have the damn thing going. i'm no mechanic but know my way around a garage, so be kind,and please forgive any stupid questions. everyone had to start somewhere. anyway the damn thing is seized. starter motor is fine, battery is good.pull the clutch in and it will move. release it and the rear locks up. any suggestions as to where to start would be most appreciated. as to why it seized, i wasn't able to get anything more than "it used to be a goer" out of my "alledged friend"

[pete376403]

Siezed as in "the motor doesn't turn over" or seized as in "the motor runs but locks up in gear"?
Narrow it down a bit first.
If the motor doesn't turn over - crankshaft / pistons / broken cam chain / broken primary chain -
If the motor runs then the problem is going to be clutch/ gearbox related.

They are a fun motor to pull apart BUT you have to remove the head and barrel to split the cases as there are four bolts underneath the barrel.
Keep track of where all the bolts go. IIRC you undo 40 bolts just to get the cams out.

I've a Haynes service manual if you need it

[dvsbob]

in neutral rear wheel rotates fine. in gear and it just locks up solid.

[R1madness]

Ok. I owned and raced these for years. They are pretty simple as far as 20 valve inliine 4s go.
Put it in top gear, pull the clutch in and get a mate to push. when you are pushing as hard as you can let the clutch out while similtainiously jumping on the seat. Does it turn over or just lock the back wheel solid? Let me know and we can take it from here.

[FROSTY:Me]

R1--mate Im not sure I'd suggest this course of action.
Im thinking one set of rings glued to bore.
My suggestion is to rip the plugs out THEN give it a little bump start -see if it turns over then.
If not squirt WD40 penatrating spray down the bores and leave overnight.
gentle bump again. -might free it up

[dvsbob]

thanks guys. i'll let you know how i get on.

[jonbuoy]

+1 Frosty, or a combo of ATF fluid and Acetone down the bores and a few days soaking before doing anything.

[pete376403]

you could also remove the plug in the centre of the left (anyone confirm??)side engine cover, put a socket on the large hex and use a bar to (carefully) rotate the motor (after the WD40 down the plugholes) Only rotate the motor forward ie anticlockwise when looking a the left side of the motor)
Pull the cam cover and make sure all is well in there, cam chain intact and so on

[R1madness]

If the rings are stuck to the bore it will need a strip and hone to get it running right along with new rings (Or you could just free it up and hope for the best but it will be down on compression and HP). All i am trying to do is determine if the engine is siezed or they are just trying to turn it over in too low a gear. What i have asked them to do will not cause and consequencial damage. But yes remove the plugs first. and give it a spray of WD40/CRC if you like. It wont hurt.
In fact put it in top and try top rotate the wheel backwards with the plugs out. If it moves half a turn then locks up chances are there is a prob with the camchain/valves.
FZR750s are very reliable in the cam/valve area so do not expect there to be anything wrong there.
Your "mate" said it was running when he parked it up. Does he have any reason to lie to you about it?
A new battery and clean the carbs, new spark plugs and caps (ngk do suitable replacement caps) and you should be away. If you end up stripping the engine give me a yell and i will pass on years of performance mods knowledge so you can get 113hp at the rear wheel. I know it doesn't sound like much now we have 180hp out of the box but on one of these it is a marked improvement from the 95hp (rear wheel) they had from new. I can get ya 122hp but the costs blow out a bit.

[R1madness]

you could also remove the plug in the centre of the left (anyone confirm??)side engine cover, put a socket on the large hex and use a bar to (carefully) rotate the motor (after the WD40 down the plugholes) Only rotate the motor forward ie anticlockwise when looking a the left side of the motor)
Pull the cam cover and make sure all is well in there, cam chain intact and so on

Hi pete. There is no bolt under the end caps only a threaded end of the crank. You would need to make a locking bolt/nut assembly to get it to work and usually you can not get enough purchase on them to beak the rings free.

[pete376403]

Oh teah, thats right - and that is what I did - make a bolt to go in there. But I wasn't trying to turn a seized motor, just rotating an engine to do the cam timing. (I put a FZ750 6 speed into my sons
FZR1000 - turned out really good)

[R1madness]

yea mate cool mod that. Then get some cams from a first year FZ750 and drop them right in. They have almost 0.9mm more lift and much longer duration. Lose a little bottom end power but good gains in the top 1/3 of the rev range. Split the head gasket into its 3 pieces and discard the outer 2 parts. Paint the remaining center part and use that as your head gasket, riases the compression nicely. oh yea, now we talking. hehehe. and 145 main jets, remove the air intake snorkel but leave the filter in place,.

[pete376403]

Aaarrrgh!!!! I had the FZ cams (I had the whole engine) and sold them. Why didn't you tell me this a year ago!!

[R1madness]

funny eh. Yamaha picked the weaker setup because "people want rideable bikes" with good mid range and are happy to give up some top end. Hence the "big" camshaft industry like yoshi being able to give ya extra hp for almost free. The hp is there you just have to find it. Often the factory parts from a different model will be able to be usd to good effect. It just takes a lot of research or trial and error to get it right.

[FROSTY:Me]

R1 Yepp I see where you're coming from. My thought though was actually HYdraulic luck from a full on lung full of shitty ol fuel or maybee just one compression ring stuck at tdc.
I think Ive still got the burned out remains of a mates FZ750 in the back yard of my old place