Need diagnosis...bike surging

[Gary_t200]

ok - Update...I took out inline fuel filter, replaced fuel and vacuum hose, snipped 1/4" off plug wires and reseated caps.

Bike starts and idles easily. Bike has sort of flat/lower power spots as RPMs rise on acceleration...especially noticible around 5000 rpms...and then will pull hard and then drop off and pull hard.

I have an 82 850 so no points...but I guess my only timing issue is to turn the backplate to the right spot. I had checked it once and it seemed right on but I can check again Sat. Does this symptom sound like timing?

I would be amazed if the carbs were clogged because I really went through them carefully (and replaced orings)...but I can redip them this fall and clean again.

Maybe gas cap vent? I havent done this before...

[btbarb]

Give it choke when you hit the flat spot and see how it responds. How do your plugs look?

[chuck hahn]

If it responds and doesnt float out with a little choke applied as suggested youll know its lean..which will mean you urn the mixture screws out. Just do 1/8 turns..run it..and readjust as needed. Better a tad rich than any lean.

To clean the cap vent, just dip it in vinegar over night and rinse well with warm water. Then blow everything dry with an air hose. should be nice after that.Also look just at the lower rim of the filer neck for a small hole..its a air vent that allows the tank to expand and retract drawing or pushing air out the gas cap venting. Be sure its open.

[Gary_t200]

Wow. This is crazy. But I decided to clean, oil, and reseal the air filter. The air filter was totally dry. No sign of any oil on it now or ever. I put nice rubber door/window gasket on top edge. Oiled it so it would slide in place nice.

Cleaned foam element with simple green. Oiled it with 20w/50. Rubbed it in good. Carefully squeezed it out. It felt much heavier. Prob had 4-8 oz of oil remaining in it. Put all back together.

I took it out. It felt very nice and responsive. Hit entrance ramp and opened it up hard. It took off. Never pulled harder. Redline in second, redline in third, approaching redline in 4th...needle buried(freakin 85mph speedo). Holy cow. It's fixed !!!! I ran 70 to 80 for the next thirty minutes. Then turned around.

Wow this bike sounds nice when its accelerating hard. Nice music from those pipes.

As strange as it seems....I think my final problem was the air filter oil and top edge seal.

Bike is like new. Time for cleanup and time to submit pictures !

Since I bought this bike and joined the site I have done following using this site, and bikecliff site:

New Plugs, recapped wires
Timed.
Valve shim adjustments
Tore carbs down, dipped, new orings, set floats, reassembled
Re-synced carbs
New petcock, new fuel hose, new vacuum hose
New stator, new gasket, new REgulator, new ground wire, extra ground wire to frame.
New AGM battery. Cleaned wire connections.
Sealed airbox, oiled filter
Changed oil and filter, changed shaft oil (rear drive had no oil and loose drain plug from some dumb PO) doesn't seem to have been driven wo oil)
Air in front fork ( seems to be holding pressure)

Had close to 500 bucks in parts. Prob 80-100 hours in labor. I am slow.

Bike runs like new. Thanks !!!

[tom203]

Hooray! these CV carbs can be finicky, but sure run nice when they are happy.

[Nessism]

Imagine that, scheduled maintenance per the manual directive fixed the problem. Who would have thought?

[49er]

Imagine that, scheduled maintenance per the manual directive fixed the problem. Who would have thought?

Sarcasm is the lowest form of wit................but I like it!

[Gary_t200]

Yeah I hear you...but I still wouldn't have guessed he oil in the air seal and the airtight fit would have made such a huge difference. It was getting waaay too much air and running way lean...which causing all my surging issues...pilot screws all out three turns and I was still lean. Now maybe I can actually tune this bike in right.