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bogs,backfires,then takes off!


Bill

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Ok...you sync'd the slides as they're shut. Did you sit there and just barely push the throttle, to make sure they OPEN at the same time? That's more critical than the bottomed out or idle setting.

 

ALWAYS change plugs after jetting and carb changes.

 

I just had my whole cub motor redone, talking ground up.

I left old plugs in, new stator, new Dyna Ignition, new powerjets installed, etc.

Took it for a quick ride, burp, pop, miss...

 

The old plugs were toast, even though they really had no ride time on 'em.

 

Put fresh plugs in, runs like a top... For 2 bucks a plug, change 'em.

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Well I got new plugs today and ran it and its still boggin and it sounds like the left side is cuttin out.The plugs are perfect color,and it idles better than ever.I was lookin around and the fuel line going from the tank to the carbs has air bubbles in it.could that be the problem?thanks

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This is totally out in left field, but...I've seen weirder things happen.

Drain your gas tank, and remove the fuel valve. make sure the bottom of the tank is clean, and the screens for the valve is too.

 

A rider here went through a million things, ended up being sand in the tank, and the filters on his valve were damn near plugged.

 

I think you're on the right track...

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Ok,I took the fuel valve off and cleaned it.It was A little dirty but nothin to get excited about.Then I got lookin at the fuel lines and the one goin from the tank to the T was kinda travlin up hill.And so was the one goin to the left carb.So I ran new lines routing them the best I could and it runs great!My only problem now is when its up to temp the right muffler smokes and pings and the left does not.But it idles fine,is that A problem.thanks

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Yep...

just reread this post, and I didn't see you doing a compression test yet. That needs to be done next.

 

A little smoke out of each until it warms up is ok...but, not one more than the other...

 

Could be a ton of things. Sticky float in the carb, air leak somewhere, crank seal starting to go...

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That should be fine to run. Next...hate to say it, leak down test to be sure.

Gonna have to make or build your own kit.

 

PM Machwon on here, he makes a great kit, or you could spend a lot of time driving to Home Depot and other stores to build your own...

 

You've gone over basics...time to get dirty now.

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You plug off the exhaust and intakes, apply about 6PSI of pressure for about 5 or 6 minutes. That checks the seals inside the engine.

 

A leaking crank seal can cause gear oil to get into the crank case, causing one cylinder to smoke, common symptom.

 

Do a search on her about leak down. RNBRAD made a very nice picture by picture info post.

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Well it ran pretty decent yesterday ,but I tryed to start it today and it fired and the right side backfired loud twice then quit runnin and the left ran fine.I know I need to do A leak down test but I dont have the cash for on right now.But what do you think about it runnin like that?thanks

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Um...not to be a smart ass...but, what do you think about it running like that?

Can't be good...period.

 

I think the more you ride it, the more damage you're going to do...and if you can't afford a leak down tester right now, putting a fresh top end on with possibly a new crank is really gonna sting.

 

Unless someone has a leak down tester they're willing to "loan" you...you're SOL for now...sorry Bill.

 

I don't think you're too far from R&B racing, his handle on here is machwon.

He sells an excellent kit, and has his own shop in the saginaw area...

 

Maybe you two could work out a deal for him checking it out for you.

 

If you think it's pricey now...it only gets worse. Something is not right...

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Fatties like a 280 to 310 main, depending on temps, elevation and air density. I'd try a 280 or 290 main and see how that works, then try dialing in the needles, 3rd or 4th clip probably. Also, Fatties tend to like a leaner pilot than say... Toomeys. You might try a 27.5 pilot, that's all you should need with those mods, 30 would be too much.

 

Hmmm, just now read the other posts.... :) There's definitely an issue. A leakdown wouldn't hurt. A compression check would be good and I'd also check the crossover tube on the manifolds to be sure it's still in check; and not in that order. Probably check the crossover tube first..... ;)

 

Edit again: 120 is good, maybe I should try reading the WHOLE post first....

Edited by sredish
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Edit again: 120 is good, maybe I should try reading the WHOLE post first....

 

Guilty myself...

 

See what I mean...sred? Too many posts in too many threads. Maybe I should try riding...well, it's been 90s here for a while, maybe not....

 

:beer:

:yelrotflmao:

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