Hi everyone. I'm new here and in dire need of help with my LG90 kids quad. I just bought this for my grandson. Ran great for about a week. Starts easy, reves good, but when you start riding it suddenly boggs down like someone turned off the fuel. I checked on some of the other posts that were having this problem. I cleaned the carb and it was very clean inside, no gunk at all, cleaned it anyway. The air filter was clean. I checked the fuel filter and lines, all clear. I checked the compression and came up with 85 lbs. I was told it should be 110 lbs. Could this be the reason for the lack of power? I would hate to replace the top end only to find out that doesn't fix the problem. I would like to try the easy fixes first before I spend a lot of money. He loves the quad and keeps asking me when it will be ready to ride. Can someone help me put a smile back on his face. Thanks!

 

Welcome to the forums.


Definitely needs a top end.

 

Thanks for clearing that up for me. Can you help me out again, where's the best place to buy these parts? How much can I expect to spend?

Thanks!

 

Welcome to the forums.
I agree, top end time.
I'd guess from $100-$150.
Try Mr.Mainstreet. he's the sponsor of the chinese forums. Prolly click on his logo.

 

Thanks for everyones help. I removed the head and cylinder and here is what I found. The cylinder was very clean and smooth except for a little carbon build up around the top rim. I miched it and there is no taper. The piston has carbon build up on top and, what it looks to me as burn marks around and below the rings. Other than this the piston looks good. There are no scratches or galling on the piston or the cylinder wall. I took pictures but I have no idea how to post them. Given this information can I assume it's safe to say I only need a new set of rings?

Thank you, Jim Roach

 

Jim, We need to know the clearance between the piston and cylinder. Above .008 I'd bore it to a new piston.
Clearances are normally:: Cast piston-.0025....forged piston-.0035

I've never been a rings only guy. I look at it like this: you take the time to take it all apart, time to clean all the parts, buy gaskets, and a $20 set of rings.
For $40 more you can do it right (IMO) with a new piston.

 

Here are the measurments: piston 2.043 and the bore is 2.048. So it looks like I'll need more than just rings. I wouldn"t even think twice if it were only a difference of $20.00. Alpha Sports Center wants $142.00 for a piston, ring, & gasket set. They also want $135.00 for a new cylinder. If you know of any other place that might have these parts let me know. Mr. Mainstreet might be able to help but he said he didn't have any Appha Sports parts currently. I understand Polarus parts might work? Any input?

Thanks, Jim

 

You don't need a new cylinder. You have a shop bore the cylinder to the new piston.
But anyways. .005 isn't bad at all.
If that's the case, You can install a new set of rings or piston/rings in the stock size (presumming that your piston is stock size now) and that should freshen it up.
You should have a ball hone ran thru the cylinder to break the glaze if new parts are used.
Call the good ppl at::
Shop Hetrick ATV Racing - ATV Motocross Dirttrack Cross Country MX XC TT | Hetrick ATV Racing Store

 

Thanks again for all the help. I'm getting closer to getting that smile back on my face. One quick question to LT80, when you say I have to "shop bore the cylinder to the piston" do you mean I have to find a piston that is the correct size to my cylinder?

Thanks, Jim

 

Would a 52mm piston be considered stock?