Ok just got my 86 250R motor back from my builder and I put it all together last night and started it. Seems to run good other then some water leaking out of the head gasket. This is a very small amount of water (about 5 drips a minute) but it still concerns me because if its leaking on the outside who’s to say its not leaking on the inside right? This is a brand new top end bored to a 265. I am running a PWK 39 with a 190/58/3rd clip/2 turns out and it seems to smoke quite a bit and also does not want to idle. FMF exhaust with a new PC 294 silencer, K&N with no lid. Does this Jetting seem to be about right? And what should I do about the heed leak? Tighten them down more and see if it goes away or replace the gasket now? I am at sea level up here in western WA.

Thank you,
Brad

 

Take the head off and copper coat the gasket, and put it back on. If that doesnt work, you may need to get it o-ringed, but it should work. Your jetting seems extremely rich, and that could be why it wont idle and smokes.

 

Im with 789 on the jetting.The same setup here uses around 165-170,55, 3rd clip.You might go to a 170-175 at sea level and the 55 pilot.

 

I know the Jetting is WAY rich. This motor has failed on me 3 times in the last 2 years because of improper jetting so I am taking no chances this time with the new top end by going extreamly rich until its broke in. I was able to fix the head leak by simply taking the cap off yesterday and re-installing it with the proper sequence and tourque, no more leaks.

As far as the jetting goes, I feel like I should be a little more specific. This is an 86 265cc OEM jug with mild porting, decked just enough to still run pump gas (92), 39mm PWK with Boysen rad valve, FMF Fatty pipe with PC 294 silencer and the air box is all the way open with a huge K&N with pre-filter. I mix MC-1 at 50:1 and like I said before the current jetting is a 190/58/3rd clip. Just yesterday I took the air screw out another turn to 3 which seemed to help some. Once I get an hour or more on this new top end I think I am going to first step down to a 52 pilot and maybe a 182 main to try that out, what do you think?

Thank you,
Brad

 

Well thats a start, but you will probly still have to come down some. Just keep doing plug chops and checkin the color. Perfect color (IMO) is light tan, but if you want to be super safe paper bag brown is good.

 

Yes, I will have to do that soon. I am a little worried about hurting my new top end though. Correct me if I am wrong but the correct way to do a plug chop would be to let the bike warm up to operating temp, then shut it down, swap out the plug with a brand new one, start the bike again and run full throttle from 1st to 3rd or 4th, and then once you are pegged in 4th, reach over and switch the ignition to off without letting off the gas. After that its time to check the plug? Is this correct or does someone have another way of doing it? Thank you very much for the info. I hope I can get this done it time for the dunes trip next weekend.

 

Yep, thats how you do it.... Make sure you have it in the right RPM range for the TYPE of jetting your doing(pilot, needle, main) For example, if your trying to jet your pilot jet dont hold your throttle wide open during the plug chop because youl get the main jet reading, and if your jetting your main dont let it put around because youl get the pilot reading. Get it?

 

Very cool, thats what I will do then. One more question, I have probally about 1 hour on the top end by now with faily easy riding. I am also useing this 190\58\3rd clip setup during break in. Whould you think this should be enough time to start playing with the jetting or should I get some more time on the new picson and rings? The only think thats been done to this motor is the top end. The bottom end probally has about 10+ hours on it.
Thank you,
Brad

 

I would wait probly 30 more minuets or at least a half a tank of gas, to be safe. After that you should be fine.