Kstar 70cc Help Needed

About a month and a half ago I installed the Kstar 70cc Treat Kit on my E50. I thought that I had did the proper breakin by doing plug chops and running a little rich. I am also running a Dellorto SHA 15mm carb 66 jet. A few days before the Richmond Rally I took off the stock SHA air filter and replaced with pany hose and put the stock black airbox back on. It did run better and I upjetted to 10 but it seemed way too rich so I went back to a 66 jet.

So on friday we travel to Richmond with the ped in the truck. I take it out of the truck and try to start it, but I am not able to start and am getting alot of head pinging. Found out that my head bolts had come loose since my friends ped pedals had been banging up against it during transit and this loosened the head. Tightened up the head bolts and 2 were stripped but it started.

Well Friday nights ride at the rally it was running excellent. I was even able to do a little blasting at times. Then it rained at the slip and slide party and while we are riding back from the party it is hesitating/sputtering and pinging at high speeds. So in the morning on saturday before the ride I retighten the head bolts but was still hesitating at higher speeds. I said Fuck it and rode to the rally. During the rally it was doing the same thing, but starting to get worse the further along the rally got. I just wanted to finish and found myself at the back of the pack multiple times. When we would stop and I would cut off my bike and then when we went to go again the was very poor acceleration, but it would get better with time. Well I finished the rally and packed the ped up. I take the E50 apart and find that the piston ring is now stuck in the piston and it looks like I was getting alot of blowBy. Piston has alot of black on the top and I probably have less than 200 miles on this kit. I just ordered the replacement piston and rings from treats, but I do not want this to happen again. I have assembled a new case with good head bolts and nuts. Here are some pictures. What was I doing wrong?

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OOOps...Pic Fail Here they are 1 by 1

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Pic2

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Pic3

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Re: Kstar 70cc Help Needed

I didn't read your post above but you should really cut better gaskets, that looks jank where the transfers are.

Re: Kstar 70cc Help Needed

Hmmm....

That's the gasket that came with the kit.

You think that may have something to do with it?

Re: Kstar 70cc Help Needed

Sounds to me like the problem is stripped studs, and only that. Head bolts should not come loose, even with something banging up against the head. That blow-by seems normal for the kstar from what I've seen; in my opinion, it's just left-over from before the kit was broken in.

Buy some new studs, then re-diagnose. That's the most glaring problem, and before you fix it, there is no way to figure out if there are any other problems.

Get yourself part number 90024A070 from mcmaster.com and cut it into 4 studs.

Re: Kstar 70cc Help Needed

well, it looks like you're jetted way way rich. Youre post was kind of confusing, when you rode the rally was it the 66 jet or the 100?

66 sounds a bit lean, but 100 is way rich for a 15 SHA.

as for the ring getting stuck, you probably should chamfer all of the ports the best that you can. (sand paper, small files, or dremel)

Re: Kstar 70cc Help Needed

I appologize. That 10/100 jet was supposed to be 70.

Can I still run the same piston? Should I try to soak it in PB Blaster to get the ring loose?

I thought 66 was lean also, but it looks rich. HMMM?

Thanks for all the replies!

Re: Kstar 70cc Help Needed

yeah try to get the ring loose and as long as its not broke, clean your shit up and run it with some good bolts!! also, those sha carbs are real sensitive to the airfilter, from stock to panty hose could be like 10 jet sizes. I think i have a 80 on mine with double layered panty hose and one screen and was low 70's with stock filter!! 87 with no filter!! get some more jets!!

Re: Kstar 70cc Help Needed

my brother was running like a 76 jet with that same setup.

Re: Kstar 70cc Help Needed

I am running a technigas exhaust also. I do have many jets for the Dellorto.

Would running too rich cause the piston head to get black like that?

Re: Kstar 70cc Help Needed

If that ring doesn't come out of there easy you might want to get a new piston, they are cheap. Gap the ring to .014 inches or there about. Head torque and jetting were probably your problem. Chamfer ports if you haven't. As much as I like air filters the SHA carbs hate them on a kit that has a broad RPM range. And kits hate SHAs in general. Figure that if you get the high end jetted right then you will be too rich in the low end with a SHA. You can still motor around like this though

Re: Kstar 70cc Help Needed

What is the process to Gap a Ring?

I think I have seen it before, but can't remeber.

Also, should I switch back to the stock 14mm bing?

It has more adjustments cause of the needle right?

Re: Kstar 70cc Help Needed

Put the ring in the cylinder sans piston and with a feeler gauge measure the gap between the ring ends. The 14mm bing might be a very little better but will have the problem of being too rich at idle if jetted right for top end. The SHA will work just not ideal.

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if you have the option i would go with the 14 bing over the 15 sha, because of needle settings. you should be able to dial it enough to have ish okay lowend and idle, while having screamy top end.

a carb that small for the kstar 70 will give you lots of torque, which is good for city riding, but the kstar reacts really nicely to a 19mm phbg and a good intake.

Re: Kstar 70cc Help Needed

the ring may just be stuck because of carbon build up. if you get the ring out, make sure you clean the carbon out from the groove where the ring seats.

your problem in richmond definitely sounds like a head leak. head leaks will rob you of low end power, and looking at the cylinder and gasket it looks like that was the case. throwing in a fresh head gasket when you put it back together will help seal it up.

i'd polish the carbon off the head with sandpaper, but be careful around the edge of the crown you don't want to round that off.

Re: Kstar 70cc Help Needed

I'd say the damage was done when we ran it with the jug loose, before finding out that is was. Remember, after that ride on Friday ( the one before I blew a hole in my case), we could move the cylinder and head by hand? Looks like first instincts were true, new studs, and make sure the whole thing is sealed up tight.

Over here trying to fix my shit too!

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