Carburetor Problem? No Power

[bullet28027]

Valves,

[bullet28027]

piston

[Rebel]

well since you have the head off it would be a really good idea to pull the valves out, look them over and at least do a hand lap on them before it goes back together. The thing is carboned up pretty heavily so clean that off and rotate the crank to see what the cylinder wall looks like, be very careful to not let the timing chain slip off a cog. Really with it this far apart, if it were mine I'd be putting new rings in, if not a big bore kit.

If you put rings in you have to hone the cylinder so it will make the rings seat.

There was a question about the springs in an earlier post, it is best to check them, take them off and make sure an inside one is not broken. Here again if you take the springs off, take the valves out and give them a once over. A hand lapping kit should be available at any auto parts house, but the tool might be a bit too big, if it is try a dart gun dart or arrow, looks very similar.

[bullet28027]

Update, I ordered a new head, gasket set and rings today, I just ordered a new head, with valves because I could see the signs of a stripped out spark plug in the not to distant future, and it also means I should not have to mess with the valves. I will probally need a lil info on the install. The first question I have is if you replace the head should you also replace the cylinder gasket as well as the head gasket because the same bolts holds them both on?

[Rebel]

If you replace the rings, you will need to pull the cylinder off and hone it or have it honed. When you pull the cylinder off that means you will need a new cylinder base gasket before it goes back together. So Base gasket, and head gasket are a must, Valve cover gasket if it has one would be good or you can just use a bead of silicone.

[bullet28027]

Question #2 Is it possible that carbon buildup could have kept the valves from seating properly, reducing compression.

[Rebel]

The only way to really tell is to take the valve out and see if it has a nice shiny ring for the mating surface. The carbon build up could be from burning oil or from running too rich. Has it been smoking?

OK, so you've got it torn down, you've ordered rings and gaskets, as well as a new head. Have you downloaded this manual found here?

scooterrebels.proboards.com/index.cgi?board=manualsreadonly&action=display&thread=47

[usfmarine]

Hey Rebel, when I install my new head, do you recommend that I change my rings as well during my next break down?

What is honing a cylinder, can I do it myself, and if I cant, how much does that cost?

[Rebel]

Marine, seems you have fewer issues, you might not need new rings. I can't give you a absolute answer. My dad was a mechanic and he always told me that if you have it apart and don't take care of something, you are asking for a problem to fix later. On the other hand, didn't you recently put a new big bore kit in yours? If the rings are pretty fresh you can skip that. If you are not smoking and not losing oil, you can skip that. If you have the original rings, might not want to skip it, kind of up to you.

Now, if I take a head off a motor, and just have to pull the cylinder off to get to the rings, I'm going to do the ring job too, it might be overkill.

Honing a cylinder is to remove the glaze that forms when the rings seat. The cylinder becomes very smooth and shiny from the friction of the rings. New rings need a rough cylinder to rub on until the two surfaces make a good seal. It is done with a abrasive stone hone or a bead type glaze buster. There are a million how too's on youtube for honing a cylinder. It is something that you can do as long as you have a little instruction. It isn't difficult.

[usfmarine]

I found a cylinder hone tool at Autozone at $25... I guess I should shop around for the rings. I'll probably hit up Carlos. After reading many threads on the matter, I guess the only slightly tricky part is to properly gap the rings.

I need a new base gasket too now.

Rebel, I don't have a big bore kit, must be someone else. If I am taking it apart this much though, I feel like I should add some displacement.

One can go from 150cc -> 160cc without having to bore out the crankcase right? Seems hardly worth it.

[Rebel]

yup 160 should go, the 170 and up can need a case bore. If you do that, it gets into a lot more work. I've heard of a 170 that says it does not need a case bore but it must have a thin cylinder wall and I think I'd think twice about that. If you get a big bore kit, they all should have the gaskets, piston, rings, and cylinder, some come with a head. Personally, I don't think adding 10cc is going to show up much in power though, and it is money better spent on the head. Now if you have a worn out piston and cylinder, get the big bore kit, it actually may be cheaper than a stock kit.

[bullet28027]

USFMarine you can find a complete gasket kit anywhere for 19.99, I got mine from Mike at buggypartsnw.com 19.99 free shipping, and the rings were 13.00 plus 2.00 S&H from scooterparts4less.com

[usfmarine]

According to all of the youtube videos I watched there's more to honing a cylinder than just running a flex hone through it with a hand drill. I am going to have to call some machine shops around here. Maybe I could find one who'd hone my cylinder, resurface my cylinder and head, and do a real quick flow test on my head. I wonder what someone would charge for those services.

[kliff]

"....hone my cylinder, resurface my cylinder and head, and do a real quick flow test on my head. I wonder what someone would charge for those services. "

hone cylinder....$25.00
Resurface head and cylinder, $30.00 ea, $60.00 total
""quick" flow test, $250-350.00"

[Rebel]

The prices kliff quoted sounds like what it should be, You however live in a place that you might see some sticker shock, I had a block for a little 2.8 liter GM motor done a few years back in Sacramento and was really shocked at what they charged me.