89 2stroke sputters under throttle

[fordnatic]

New member, long time lurker. I need some help, i am running out of ideas. I have an 89 that ran great but now i am having what the best i can describe as a sputter or like a miss at full throttle. A little history. I have done a top end and replaced the crank clutch side seal. new fuel pump, cooked the muffler. cart was running great but i had carb bowl leaks. I couldnt find the right gasket or o ring and decided to go ahead and order the thunder jet carb from buggies. Basically bought this to stop the leaks. the original carb has been apart and blown out many times. Put the Thunderjet carb on and cart wouldn't fire. Took carb back off and noticed the jet sizes were larger than the original. I was taking the cart camping so in a hurry i took the bowl o-ring and the bolt gasket from the new carb and put them on the old. This stopped my leak and was the most expensive o-ring and washer ever! Now after a few weeks the cart is hard to start and just keeps cutting out/sputtering, then run and over again. It does get up to speed and seems like fuel is starving or spark is going away. I have since torn the old carb down and blown out everything. When it cuts out (for a second) its like the brakes are tapped then fires right up. Its not backfiring, the butterfly is closing completly when i am off the gas. Could it be throttle plate or spark? Seems to run better in reverse but i haven't taken it around the block! Any ideas would be great! This cart was a pig when i got it, beat up and ugly but ran like a champ. Maybe i shouldn't have painted it . Thanks Jeff

[Dave Box]

There are many reasons for this to happen but here are two that are easy to check.

1. A partially blocked fuel filter

2. A blocked breather tube from the top of the carburetor.

Dave

[fordnatic]

Thanks Dave. I consider myself a gear head but sometimes I wonder what the heck I did. Took your tips. Cleaned the carb and then checked the fuel flow. Right away i knew something was wrong with just a trickle. Pump was replaced in July, clutch side crank seal in August. Just a flow out of pump. Somewhere along the line i put two fuel filters, one after the pump before the carb but reading i see that could be an issue so i removed that and while replacing the filter coming out of the tank i realized i put it in backward (WTH). Anyhow one new filter in the right direction and still low flow, not squirts. Thinking the flywheel seal now. One other question. What is your knowledge on the "Thunderjet" carb sold on Buggies Unlimited? I bought this last summer to replace my BV-18 and the jets are definatly smaller. When i called them about it they referred my to some guys in Washington who handle mostly older Harley's and said this is BU's problem. Which i agree. Just trying to find out the correct jet sizes for a bv-18 on a 3pg. Thanks

[Dave Box]

I think that you are on the right track with the front crankshaft seal. There is some anecdotal evidence that as the seal starts to wear the cart will run better in reverse (you state this). The reason is that the engine spends maybe 99% of its life in the forward direction so when you reverse, the crankshaft scuffs up the rubber and gives you a better seal.

With regard to the Thunderjet, I have to say that I never comment unless I have been there, done that so the simple answer is that I just don't know. That said I am not a fan of BU and quite often you will see similar tales of after sales service here. I would however point out that your 3PG should have the larger BV-24 carburetor. The BV-18 was standard to the 9hp 2PG.

Dave

[fordnatic]

Thanks for the carb info. I am looking at a BV24 on the web and the throttle connection looks different than the BV-18? Was it common for an 89 to have the 2pg carb. I don't think this cart was changed from new but who knows. Will the BV24 make a significant diffence? I would think so being 1/3 larger per what i am reading. thanks.

[Dave Box]

I guess we should be sure that you do in fact have a 3PG. Is the muffler vertical or horizontal? Do the clutches align side to side or from rear to front?

Dave

[fordnatic]

Horizontal across the front and the clutches for front to rear. 3PG right?

[simple man]

Don't mean to hijack your thread, but what do you mean by " cooking the muffler "? Can't see where it would taste very good!

[fordnatic]

Take the muffler off, get a good bonfire going, throw it in. Let it cooked for a while until good and hot and smoke coming out both ends. Take it out and shake and bang all the carbon out of it. rUns way better and the firewood, beer and time are alot less then $700 for a new muffler.

[Dave Box]

... and it does sound like you have a 3PG with a 2PG carburetor.