Planet Minis

spiralsun1

I am experiencing technical difficulties. See if you can figure out what this is, I cant! OK, I put in the larger jets on my 20mm carb on my crf70 88cc with race head (see my earlier post)-- it did not help. It runs fine at idle -- perfectly smooth. Then it runs fine with the throttle just barely on. Anything beyond that and it's like it just completely loses power the more throttle you apply with only little blips of power here and there, it just breaks up and runs really rough bogging down horribly occaisionally punctuated with very loud backfires. I changed the jets up, pilot jet, main jet, and dropped the needle clip all the way down -- still runs super super bad at anything above idle or barely throttled on. it sounds like it is running out of gas -- it just completely loses power at times then hits a tiny bit, but slows almost to a crawl wide open with huge backfires. not good. Any ideas?

Help please if you can, I'm really at a loss. Could it be a failure of spark advance? Honda said the valve adjustment and timing are fine. I thought maybe I put the cam in wrong, but how could it run perfect at idle if so? Very strange. I know that from idle to 1/4 throttle is the pilot jet, so it does seem like a fuel or jet issue, but I put in a 92 main and 38 pilot and it did not help. I dropped the needle clip all the way down too, no effect.

Do I need a MUCH larger main jet? I heard someone here drilled out a jet to 110....? I just don't know. Someday I really want to ride this bike. It has been a year.

BlackBeard

i would purchase a new carb, make sure fuel is coming out of the inlet hose and be good to go

project-c2

Check your timing again. Post pics if can. I drilled out my main to 110. But with the stock jets it ran okay, just on the lean side. Line up the crank with the "T" mark. Also, shorten your hose to the carb and make sure no kinks. Another thing, you didn't put a hose on that brass pin sticking out did you? The upper one on the other side of the carb...

spiralsun1

Hey, thanks for the replies people. I have just the fuel line going into the carb, that's it. What else do I need?? There is no vacuum advance or anything is there?

spiralsun1

So you think the carb may be defective? Does that happen a lot? Can I just open it up and fix it...?

spiralsun1

OMG, nothing works. How can it run so great at idle and not at all above 1/8 throttle... ? I tried timing chain, jets, etc. with no effect.

spiralsun1

Thanks for all your suggestions / help people! But guess what?

I FIXED IT!!!!!!!!! IT HAD NOTHING TO DO WITH THE NEW ENGINE / CARB I PUT ON THERE ODDLY ENOUGH.

FOR SOME REASON, THE SCREW THAT THE GROUND WIRE HOOKS ONTO UNDER THE GAS TANK ON THE FRAME BACKED OUT AND WAS LOOSE (ALMOST FALLING OUT) AT ABOUT THE SAME TIME I TOTALLY REBUILT THE ENGINE!!!!! WHAT A MIND-NUMBING COINCIDENCE! THAT WAS THE WHOLE PROBLEM!

At Idle the engine did not produce enough vibration to make the connector and screw dance around and lose contact -- only when I really hit the throttle.

After a year and a half, just tightening a screw made it run PERFECTLY. It has TONS of SCARY power -- I wiped out first thing because of the physics-defying power burst, and my leg still hurts, but it is sweeeeeet. A mark of sheer joy now.

I would say that the money I spent on the TB 88cc kit was the best engine money I ever spent. Runs better than new, idles smooth, starts ridiculously easy with no effort.

I'M TOTALLY IN LOVE WITH THIS THING.