New 70cc K-Star

I have posted forums mentioning my carb spits back gas through the air-filter side when I run my engine at all throttle positions. To mention my K-Star was ported by me and I just went at it with a dremel without any drawing or mathematics. Can this shitty port job be the source of my problems? I have replaced gaskets, Started with a SHA dellorto and switched to a clone 15mm Bing,intake, airfilter, changed timing, even improved my first casematching. I've haven't replaced these but I don't think they are the problem, Head, and pipe. I'm just planning on buying a new 70cc K-Star kit and just chamfer and check the ring gap. Thank You

Re: New 70cc K-Star

Probably Fred /

Ya I never had any problems like you did. Ya its possible you made a door stop.

I'd have to see it/try it out. Sometimes spacing the base just 1 mm different could help stop the blow back

But for other then clean up and chamfer I leave the ports alone on the inside and don't carve the piston skirt either.

I kit for reliable street bikes not a race track though.

Re: New 70cc K-Star

Salsa Valentina /

Yea just want a nice cruiser without getting soaked in gasoline

Re: New 70cc K-Star

All the Kstars do that. If you didn't alter the intake timing then its operating just as it should

Re: New 70cc K-Star

Salsa Valentina /

So its normal for the k-star to do that? So what you're telling me is that if I alter the intake timing I can stop the blowback?

Re: New 70cc K-Star

yeah, they just do that. think about what's going on in there and it just makes sense. some dudes i know say running a few inches of "snorkel" out of the carb will help this and even increase speed. i liked mine how it was. it would make that nice white tornado looking gas vortex when you wot-ed from a stop. i tried and tried to light that shit but it always blew out the lighter.

if you don't like it, i suggest a reed kit. they still blow out a little bit, but not nearly as much.

Re: New 70cc K-Star

Salsa Valentina /

I'm on a budget but it still kind of upsets me that all the K-Stars do that

Re: New 70cc K-Star

Probably Fred /

Salsa Valentina Wrote:

-------------------------------------------------------

> I'm on a budget but it still kind of upsets me

> that all the K-Stars do that

They don't all do that

I've never had problems but I base space correctly

Re: New 70cc K-Star

Salsa Valentina /

What's your recommendations on base spacing?

Re: New 70cc K-Star

Probably Fred /

You didn't space your base?

You are supposed to space the base so the transfer ports are full open with piston @ bottom and the piston ring is not exposed in exhaust port usually around a 2 mm metal base and a base gasket on each side so around 3.2 mm.

Then you have to deck the cylinder a few mm or mill your head.

You didn't do any of that Huh?

Re: New 70cc K-Star

Salsa Valentina /

I did but I don't know how much spaced up or down

Re: New 70cc K-Star

You need to read more carefully to what people are telling you

Re: New 70cc K-Star

Salsa Valentina /

Yes I do

Re: New 70cc K-Star

Piston port cylinders barf fuel back out. Period.

Also, porting without knowing what you're doing is a great way to learn. Teaches you a bunch of 'what not to do'.

There's a Sea of knowledge about intake tract length, airboxes, filters, etc. Today I shortened up the After carb intake tract on a Hero Puch 65cc by 1.5" and the 'airbox' tube off the back of the PHBG by 3", and it changed the entire personality of the bike.

but to answer your initial question: You can put an 'air box' on the mouth of your carb to capture backblast, but it Is going to affect your fuel air mix.

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