1986 250r Jetting at 5600' elevation

[d.palmeri]

I have an 86 250r and I live at 5600' elevation in Southern California, so the temp is around 50-65 degrees in the winter and 70-85 degrees during the day and I have no top end, it stutters when I'm wide open, almost like there's a govenor but when I'm in lower elevation it runs better but not great, like it should. I read a thread the other day with someone with a similar situation and the cure was to clean the carb. So yesterday I took the carb out and apart; it was spotless but I cleaned it anyway and still the same problem. I have a FMF Gold Series Fatty Pipe and FMF Powercore silencer with the airbox lid and snorkle pipe to the frame removed. My jet sizes are stock (42 pilot and 145 main) on the 34mm flat slide Keinin. I'm thinking it may be a jetting issue but don't know what size I should switch too. Any Sugestions? I do have this hour meter/tach but don't think that it has anything to do with a rev limiter.159281
I would also like to ride at Glamis so would I ahve to switch the jets again for the lower elevation? Please help!!

Thanks in advance

trailpro

trailpro trailpro
Keep Ridin Dirty

[d.palmeri]

I forgot to mention that I have a K&N filter with an outerwear, but removed the outerwear due to it deteriorating. with plans to put a new one on.

[rjs89ia]

Without looking at the manual I couldn't tell you exactly what size of main jet to run but going a few sizes smaller probably would help out tremendously. Safest way to do it is come down one size at a time get some new sparkplugs for each jet size and do a plug chop and see what the color looks like. Light brown is the ticket, if you need info on how to do a plug chop or a link to the service manual just use the search bar and that should lead you to what you need.

[d.palmeri]

Damn I'm really forgetting alot of information tonight. I'm also running 20:1 as the recomended sticker says. Should I be running a leaner ratio. When I pulled my plug the other day there was a sh*t ton of carbon build-up. So I cleaned it and there was no difference in the performance. Running a NGK plug.

[d.palmeri]

I'm not sure what a plug chop is? Sorry kinds new to the whole thing, but mechanically inclined. Thanks for the response though; I really do appreciate it.

[4x4van]

Run a good quality oil at the oil manufacturer's recommended ratio; I run Golden Spectro at 53:1 in my 85 250R; have since it was brand new. Many run other good quality oils at 40:1, 30:1...IMO 20:1 is too rich for any oil.

You have a K&N, a pipe, and an open airbox. No way should you be running stock jetting (when my 250R was new, the first mods I did were a K&N and open airbox; that alone required 2 sizes larger on the main jet). All of those things combined would normally result in needing at least 2-3 sizes larger than stock on the main jet. However, because of your elevation, it could likely run too rich with larger jets, so stock jets might be OK in your situation, or just 1 size larger.

Another thing to remember is that running a rich oil/gas mixture (your 20:1) translates into leaner carb jetting; changing to a quality oil at a leaner fuel mix will actually richen your carb jetting. Read my post here (post #16) for more info on that: http://www.3wheelerworld.com/showthread.php/53212-All-About-2-stroke-Oil-Ratios.-Interesting-find/page2

Once you decide on an oil, stay with it. At that point, you can do a plug check and start to dial in your jetting for your elevation. BTW, once you get it running good in Lake Arrowhead, you WILL have to rejet for Glamis, as it is at or near sea level.

[d.palmeri]

4x4van Thanks for all the information. That was a good read. I'm running a Castor 927 Pro Series premix oil. The guy at the bike shop recomended it. The bottle recomends 20:1 to 60:1. So I will try the 40:1 that you recomend and see if that makes a difference. I am getting some spooge at the exhaust joints. I will also switch to the Golden Spectro.
Thanks again for all the help.

[kevin]

oils have come along way since they made these 3wheelers, 40:1 is what i run with a good synthetic