New 330 bigbore Big Probmels Need help

[330BigBoreR]

Here is the deal I just bought my first 86 250r and it came with alot of new parts and it was all in peces. it came with a extra motor with a aftermarket crank (hot rod) and a esr 330 big bore kit with the cylinder spacer and a esr head. and a new piston and all of that good stuff.

Well while I was waiting for the coil to come in I did a compression test to figure out what kind of fuel i needed 93 or 110 and it only had 120 psi of compression with all new parts. so i was worried but figured maybe the rings needed to seat and it would go up. well today the coil came in and i installed it and put 2 gallons of 93 with castor 927 mixed to 32:1 for the break in. the bike started on the second kick and idled perfect so i did the 3 heat cycles everything was good. then i drove it around the block about 3 times adjusting the throttle but never going over 1/4 and then it just stalled. i choked it and it started right up brought it back home and the plug was fouled i put a new plug in it and it will start but won't idle and it bogs real bad when you give it any gas.
the compression test this time was 95 which i don't think is anygood is the topend toast what is causing the compression to be soo low? I checked the head o-rings and they looked fine and there was a light layer of oil on the head and piston and the piston is pretty tight in the cylinder. I put the head back on and still the same thing.

I took the carb apart and the specs on the carb are
Model# S65 A2 qev
Main 160
Pilot 48
and the needle is either a GEK or a DEK I forget now but I know that the last 2 letters were EK

[darren250r]

Is the bottom end from an 86(short rod) or 87-89(long rod)? If its long rod, then it sounds like you might have a 87-89 piston and a spacer plate. Easy way to tell is to take off the head and slowly bring the piston to the top of the cylinder. The pistion should come all the way up and be basically flush with the top of the cylinder. If it comes up 1/4" below the top of the cylinder, then you either need to get an 86 piston or take out the spacer plate. The 86 piston is taller above the wrist pin than the 87-89.

If you have the stock short rod 86 bottom end, you need an 86 piston with no spacer plate. If you have a long rod 87-89 bottom end you either need an 87-89 piston and no spacer plate or an 86 piston with a spacer plate.

Hope its not too confusing, but do some searches because I know it has been explained more clearly. Basically if the piston doesn't come all the way up you either need to remove the spacer plate or get a taller(86) piston.

Darren

[330BigBoreR]

I should have mentioned that the piston does come up flush with the top of the cylinder that is what I don't understand. and i have the esr head where you can change the dome do you think that it could be that low because of the dome???? or could it be a gasket in between the case and cylinder. I pulled the head and the o rings look like new and there would be water in the engine if that was leaking. and thanks for the info on the spacer that was the first thing that i thought it was too

And how do I find out what carb I have if I don't have the clymer manual?

[Qracer]

Are you holding the throttle wide open when you are kicking it? Are you kicking it until the gauge stops moving? If I kick my 500 over like I was trying to start it it only has about 100 psi. If I hold the throttle open & kick it for all I'm worth it has about 160psi.

[250r4life]

Originally posted by 330BigBoreR
I should have mentioned that the piston does come up flush with the top of the cylinder that is what I don't understand. and i have the esr head where you can change the dome do you think that it could be that low because of the dome???? or could it be a gasket in between the case and cylinder. I pulled the head and the o rings look like new and there would be water in the engine if that was leaking. and thanks for the info on the spacer that was the first thing that i thought it was too

And how do I find out what carb I have if I don't have the clymer manual?

no... any dome that they would sell would not be for compression that low... something is not right...

you said you just rebuilt it with a new piston, rings, and bore?

[hang1p]

check your squish band not by eye balling get a acutal measurment and what number is on your dome when i got my new 350 cyclinder they gave me a the wrong one giving me a 120psi reading i got the 55r dome gave me about 150psi i should be at 175 so i think my squish is to big but it runs so damn good I haven't bother to check it

[330BigBoreR]

yeah it has a brand new top end cylinder and all

how do i check my squish band do i put a peice of clay or somthing on the piston bolt the head on and turn the motor over??? I have never done this before.


I went out today and it won't even start now it kicks back like the timing is off.

[330BigBoreR]

alright today I put 110 in it and messed with the carb and now it is running but seems really rich it idles but when you give it fuel it is really hesitant to take it. mhow do i find out what carb i have it has this stamped in the side S 65A2

[86 Quad R]

you can use putty but the most effective thing to do is to use thick solder that is inserted through the plug hole perpendicular to the engine.

this is done more effectively with the stator cover removed.

to do this you get the piston almost to TDC and slightly angle the solder so that it makes its way to the very edge of the pistons edge, touching the cylinder wall.

after youve accomplished this you continue to roll the engine over using the fly wheel. you'll experience a resistance but, continue untill your past TDC.


roll the engine back, repeat this back and forth until there is no resistance. you are now ready to measure the thickness of the solder.

[330BigBoreR]

alright i will try that and I spoke with esr and I have the race fuel head and now it runns with race fuel. and I found out that the carb is a 35mm PWK

[sandspanker]

:) you need at least a 38 pwk:macho

[330BigBoreR]

already bought a 38mm airstriker but now i am haveing problems because of the exhaust orings are torn so I am now waiting on those and new springs