Still a Mystery with top end sputtering

[fxnteeth]

OK guys here is what I have done. I live in Central Louisiana, 38mm airstriker on an 85 250R. Middle position, 170 main with a perfect plug chop. stock pilot. New unifilter airfilter, with no box. FMF fatty pipe and silencer. Motor is a 260 new. Because of the top end sputter, I was suggested to replace the ignition system. I did this even the stator. Still the same. It idles perfectly. Everything is great until I reach high RPMs. It is a definate sputter. I have played with the jetting, but it really didnt run any different. As stated before the plug chop has a nice tan color. Pulls well from Idle. I was running 110 octane at 32:1 klotz techniplate. I changed to 93 octane, no difference. WTF else could be causing this. Please give me a starting point. Oh yea, I also have brand new V-Force 3 reeds and cage. HELP!
thanks
Jarrod

[fxnteeth]

bump!!!!?????

[Slingblade]

Well , you've covered just about everything. I'm pretty sure this has been suggested, but did you try gapping the plug down to about .015?

[fxnteeth]

I have not tried that. Will try tomorrow. Any other suggestions?

[gotballs 250r 82]

is your air filter good and clean could be starving for air at top end

[beets442]

Hows the timing, petcock clean,gas cap vent, bowl over flow clogged, recheck reeds mateing surface and tension?

[bcredneck]

have you tryed a timing strobe light your timing might need to be advanced every part you installed is for topend power so the timing has to be changed to match the motor it probley revs higher now so the stock timeing curve wont advance as much as it needs to on some motors you have to mod the stator plate or move the pulser coil

[fxnteeth]

This is probably a dumb question, but how do i use the timing strobe to check for accuracy and how would i mod the stator plate or move the pulser coil. I have seen a timing plate for the 250R. Could this be used.
thx

[Dirtcrasher]

It doesn't get done and is not the source of your issue. We'd all have adjustable plates if Honda wanted timing screwed with..........

[NOS_350X]

Run it some and make it sputter, then pop off your radiator cap and see if it is foamy. If it is then replace the headgasket.

[oscarmayer]

check the head gasket. mine is a 4stroker but my HG blew and had the exact same issue. i discovered by accident.

[Ironbnder]

How about you just sell it to me. I am 10 minutes from you whenever you are ready.

[OZQUAD44]

I doesn't have too much compression does it? That would give you significant detonation at high RPM or load. Which could be confused for spluttering, alternatively

If the static timing has too much advance you will also get a similar phenomenon.

[Ladnerboy700]

U say played with the jetting? My tri z did the same thing and I was off a lot on the main..there was no detonation so the plug color didn't change...try going way bigger....those carbs have to have negative pressure (air box) jetting makes up for this....

[atcmatt]

Sounds exactly like what mine is doing mate. Only wish I knew what it was! I have tried eveything under the sun and it still wont run properly! I think Im going to get rid of my big bore and go back to the stock cylinder. Best of luck with it and let me know if you find something that fixes it!

[bcredneck]

this is a long read but it will help you alot if you use after market parts on your two stroke http://www.bikechatforums.com/viewtopic.php?t=25415&view=next

[fxnteeth]

DirtCrasher, what do you suggest may be the issue and does anyone else want to chime in. MEGA frustration
thanks

[j4duncanr]

i had a lt500 doing the same just sputtered on top i kept rejetting finally i was soo low i knew something else was going on turns out center cases gasket was leaking pulling transmission fluid into motor cavity.is this motor ported or just bored?if itsstock just bored id get that 38 off and go back to 34mm.also and this is a long shot i wonder if those new reeds are not holding tension at wide open.

[Dirtcrasher]

DirtCrasher, what do you suggest may be the issue and does anyone else want to chime in. MEGA frustration
thanks

I'd go richer and leaner, record the results, plug color. Just don't beat the snot out of a white plug................ - Just keeping trailprotrailprotrailprotrailprotrailprotrailpro with the main. Then F with the needle etc. One thing at a a time.

Suddenly you'll say "dam I'm lean, "or I'm way too rich." You'll get it/feel it. It's gotta go up, go up.....

[j4duncanr]

i wonder if your float level is off.too.i wouldnt rule that out either

[cr480r]

leaking choke valve?

[ceaserthethird]

If you can't figure it out take it to a shop, Did you break the Motor in ?

Who did the Rebuild on the motor ? And Some Detail's of what was replaced ?

You'll Need to do a Compression Check Cold & Hot.

What needle do you have ?

[fxnteeth]

The motor is ported not just bored. I have not run a compression check or checked the float level.
Will try
thanks again