New ATC90 Project

[Frankencelery]

Hi all...great site! I just picked up a "hybrid" ATC90 that I'd like to get running. The frame says US90, the engine says US90E, but the seat and fenders are from a '78, and it has a headlight, which I don't think the older ones had, and the carb has the altitude compensator, which is older model. Hence the term "hybrid". Assuming that it ran at one time, but does not currently, I bought it for next to nothing and began working to get it going again.

Cleaned the gas tank and carb. New fuel lines and installed filters (tank is rusty). Replaced plug and points. Has spark, but won't start. Ran compression test. 60lbs. Not good. Checked valve clearance= ok. Squirting oil in the cylinder brings the compression up only very slightly. So I'm expecting to have to do a top-end rebuild. I've never done anything like this, and I have a few questions:

1. Does this sound like the likely problem? Is it usually valves causing it, or a leaking gasket somewhere?

2. Are the parts still available? I'dl love to find a top end rebuild kit somewhere, if such a thing exists. I need to call Honda with the engine code to find out exactly what year it is, before I start trying to order parts.

3. Can joe sixpack (that would be me) do a job like this if he has no experience but a little mechanical ability, and a Clymer manual?

Thanks in advance for your input.

[Frankencelery]

I have this annoying tendency to reply to my own posts. At least I keep myself entertained!

Re-reading my post from last night reveals some mistakes. I know some parts are mixed from different years, but I was wrong about a couple things. I'm still trying to work out the identification of what I have.

1. The VIN is US90-207588. Based on what I've read, that would make it a '72 or '73. The front fender is metal, and the rear is fiberglass. It has a headlight, which I've discovered was only absent the first two years.

2. The TANK (or at least the tank decals) is from a '78, not the fender and seat. The fender may be original.

3. I meant to say that the carb with the altitude compensator was from a newer model, not an older one, but I really don't know what year they started using that. Seems like I read '76 somewhere, which was why I was thinking that.

4. The handlebars have the release lever to rotate them sideways, and the foot pegs fold up.

Maybe with this info somebody can help me nail down the year.

Thanks again!

[brapp]

i'll sell the 90 ihave for fix of parts, i have abotu 140 wreaped into it.

[Rex Karz]

dratv.com has all kinds of stuff for 90's

[Yamahauler]

I'd say you could do a top end job yourself. I had no mechanical skill at all before I came to this site. After being here since september, I've learnt quite a bit, from reading others posts and working on my bikes.
I'm in the middle of a top end job on my yamaha 200e. Its pretty simple.

I say go for it.

Low compression can be caused by a bad gasket, bad rings, worn out cylinder/piston. Thats what i can think of off the top of my head.

[MTS]

Did you to the test with the throttel wide open..? but a top end is easy on it, ther is a gasket kit for them...versah but i wouldnt use it,...tried it and the gaskets where poor quality, phone your local honda shop, you can get all the gaskets rings, bout everythin you need for the rebuild for 100$ assumin that you dont need a bore and bigger piston...if so add 50-60 bucks, clymer manuels are great, you would have no problme doing the rebuild if you have one.

[Frankencelery]

Well, I got the engine out and disassembled, which was a much easier job than I expected. I have the cylinder and head to the machine shop, and the guy already said they were in really good shape, so I'll probably end up with a .25mm overbore. Strange that the compression was so bad, but maybe a gasket was leaking.

I already use dratv.com for the parts I break on my buddy's ATC185s. I rolled it a couple months ago, and had to buy some parts. I have to wait until I hear back from the shop to know what parts I'll need. I know for sure I need a chain and sprockets, and I badly need a seat as well. The seats are going for absolutely stupid prices on Ebay. I was bidding on one that went for $191.00! I've yet to find anyone else selling seat covers and replacement foam for these.

[nouseforaname90]

As for the seat, I know what you mean. I was looking for a seat cover for my 250SX, and couldn't find one for under $40. (Not much.. but I'm cheap, ok?!?) So I went to my local crafts store, got some nice seat fabric, and did it myself. Just go get some good fabric that you would like on the seat, and use 1/4 inch staples. It took me about 2 hours to do, but it looks great (it looks like a new seat.. no wrinkles or anything.. i was proud of myself), and it only cost me 7 dollars for a whole yard of the fabric, and a yard of fabric can do two seats.. so it saved me about 37 dollars..