need help

[CODY_M11]

ok so i just got a 89 250r. had a fried piston and cylinder was bored 50 over when i got it. i honed the cylinder out put all back together and she fired right up. the first problem i had was it was folwing plugs like crazy. changed main jet and it fixed that problem. second problem is 1/2 to 3/4 throttle it seemed like it was revving out like a 4 stroke and lost all power. after i changed the jet it only does it in 1st and 2nd gear now. and it will just die after couple minutes of riding now. like it looses all spark.

so y does it loose power after half throttle and y does it die?

[All250R]

If I were you Cody, I would set all your jetting fat, all at once, make sure your plug in NGK is a 9 if possible and start with a compression test on a new set of rings with a piston set at the proper clearance for a healthy engine. If the timing is adjustable (stock is not), retard it to stock setting.

Make sure the engine will run without seizure (major or mild) and does not lose compression obviously after solid run time. Fine tune the jetting and/or trouble shoot your electrical system from here, now that you're confident you don't have some other mechanical problem.

You have to have confidence that the engine is going to stay together first to rule out other problems NOT related to jetting before you try to jet the engine. Does that sound reasonable?

[CODY_M11]

Ya that all sounds reasonable. What is a good starting point with the jets? Spark gap? Fuel mixture? Im running stock main jet and 48 pilot. Running a 9 spark plug. I tried to gap it a .18 like ive read alot of ppl on here run. It wouldnt fire at that gap so now im running .34 gap and it fired. Im currently running 50 to 1 fuel mixture. Remember its bored 50 over with a aftermarket lrd pipe. Thanks for all and any help guys.

[CODY_M11]

Also wat is the compression on these engines suppose to be?

[86 Quad R]

a healthy stock engine (with stock head gasket) should be no less than 160 or so.

are you running a resistor plug? if so get the non resistor and try it at .018 - .022. i'd also pull the stator cover and inspect things there. i've seen rust setup and retur spark as well as bad or curroded<sp plug wire ends(at the cap). hope this helps :cool:

[All250R]

If you're running the stock carb (34mm PJ) I'd start with a 158 main and the 48 pilot with the needle in the middle or next lower groove.

I forgot to mention you should do a leak down test. The service manuals assume your gaskets and seals are all in good shape and mating surfaces aren't damaged or warped. A leak down test will tell you if the crankcase is compromised with an air leak which obviously will throw off your fuel:air ratio. It's important to know that there is no leaks in the engine, for any engine, but especially one that's having issues..

I recommend going back to stock in the ignition system. When you start with a known good baseline, you don't have to worry about confounding variables throwing off isolating an issue or performance improvement. A stock compression engine should be able to be gapped at .028 without any issues at all. If it won't fire, you should troubleshoot why and fix it before moving on. Diligence and discipline is the most trustworthy way to get your engine ready for running and the next performance improvement(s).

I hope that helps.
Jason

[cdrookie]

also make sure that the float is set correctly and the petcock isn't clogged