ATC 90 performance upgrade possiblities

[turbowrenchhead]

I recently purchased a 1978 ATC 90. My neighbor and I bought it to pull an ice shanty. We went through the bike and fixed many little things that had been neglected. We got the bike running half way decent. The carb that was on it looks like its off a 110. So my first question is it a 16 mm or a 22mm carb that came with the 110. I completely disassemble it and cleaned out all the jets with seafoam. I blew them all out with pressured air. When I got the carb back on the idle was all over the place. I would get it to idle and then when I put it in gear it would die. We took it out on the lake last sunday and it did pull the shanty but in low 1st gear. I had to give it a push to get it going. After driving it around for half of the day the idle seamed to get better. It would only die once in a while. It seemed like the carb would load up and idle down and die. Second question. The screw that is left of the idle screw is that the air mixture screw? No matter how much I turned it, it didn't make a difference either no load or under load.
I have been doing some research to see how I can make some more power with this bike. I see there is a 54mm piston with a 9:1 ratio. I called around to find out who can bore and hone. One shop told me it would have to re sleeved. Is this true? Another said it would cost $250 if it was Nickelsel plated. What type material is the cylinder? Can it just be bored and hone without other work needed to be done to it?
Can the head be milled down for higher compression? How much can it be milled safely with the big bore piston that has a dome? Can you use the stock head with the bigger piston?
Beatrice told me that a cam, piston and carb would run $135 and would make a big difference in power. Has anyone done this to their trike? What other things should I know about before I go ahead with this upgrade?
Can the valves be adjusted? If so how does one do this?
What 90 and 110 engine parts are interchangeable? Are the heads the same?
I am a automotive mechanic, so I have a basic understanding of engines. I appreciate any information to help me better understand this little motor.
Thanks in advance for the help.
t

[Vealmonkey]

Welcome to the boards. You are going to be very busy here soon. LOL First you need to look around here and download you a service manual for your trike. You need to do a major tune up. Change oil, clean filter screen, new plug, set valves and set timing. To do those things you will need a manual, oil, plug gasket set and a nice set of tools. You should also replace your points and condenser while you are at it. Once you do that, you should set your valves and check your timing. That should help alot. Also you want to check your front and rear wheel bearing to make sure they are in good working order and that is as simple as raising the front tire off the ground and spinning it and making sure that there is no unnecessary drag or noise. If your bearings are bad, you will know. Same for the rear, but you could also have the chain dragging on the system or the rear brake dragging. You will probably want to spray you chain down real well with some PB blaster or something like that to make sure it's not all rusty, which will cause drag on the system. You may need to adjust your rear brake, the manual will explain how to do this and it's pretty simple. You may also have to or at least you should adjust your clutch and the manual will explain this also. These things won't cost alot, it will just take some time, but the little honda 90 engine doesn't make gobs of power so you need all your systems working as well and smoothly as they can. Get Busy! LOL Have fun and lets see some pics. Let us know what you find as to how all your trike systems are working. Also, put a good amount of seafoam in your fuel tank and let it work it's way through the carb as you ride, it will help some. Also you may want to purchase a couple small inline disposable fuel filters to catch any stuff that may be hiding in your fuel tank. If you need to replace bearings or chain or anything else, the manual and people on here will be glad to help. Now get those wrenches turning. And remember, most everything on your engine is aluminum, so don't overtighten nuts and bolts and strip threads out.

[greenhuman]

The standard 90 cylinder will easily take a 54 mm high top without sleeving. They are cast iron so they rebore just fine. Don't shave the head.
While the head is off, have the valves checked and lapped in and the exhaust valve seal replaced.
Look for a 22mm carb off an old Honda SL/XL/CB 100 and match you inlet manifold to the carb. A free flowing larger diameter exhaust should be fitted while your'e at it.
You will be surprised at the difference these mods will make.

[Mr_RPM]

The standard 90 cylinder will easily take a 54 mm high top without sleeving. They are cast iron so they rebore just fine. Don't shave the head.
While the head is off, have the valves checked and lapped in and the exhaust valve seal replaced.
Look for a 22mm carb off an old Honda SL/XL/CB 100 and match you inlet manifold to the carb. A free flowing larger diameter exhaust should be fitted while your'e at it.
You will be surprised at the difference these mods will make.

do those carbs bolt on? what do u mean by "match you inlet manifold to the carb" id like to know all my options for carbs on the 110s, im doing a hop up myself. what has worked in the past, and just stuff like that.

[turbowrenchhead]

I typed out all this info, I submitted it and it bootted me, ARG. So I will have to type this again.
Here is what we have done so far. Disassembled, cleaned carb, tried to adjust, not much luck with that. Why doesn't the carb air mixture screw do anything? New plug gapped at 0.030. New clamp style air filter. Cleaned gas tank filled with 93 octane for the additives and added 3 oz of seafoam. The high low was stuck in low. Removed cover and pin was seized. Cleaned and lubed now working fine. The rear brake was seized, cleaned and lubed arm, adjusted brake, no drag now. Removed tired, sandblasted rims, remounted inflate to 5psi. Ice studed rear tires, Have another tire and wheel coming so I can run 1" spikes in it. Front bearings are fine, tire spins easily, rear seemed fine, would have to remove chain to know for sure. Dont hear bearing noise while operating. Drained really black oil, cleaned bottom out with gas, blew air through, filled with 10w30 w/ 1oz of seafoam. Ran carb cleaner through top end. Lubed chain with white lithium grease. Added a 55w headlight. Wired it to a yellow wire that disconnected putting out 12 volts. There was a brown wire next to it. What is that for?
The exhaust was rotted. I pulled it out and put just the head pipe back on with the end flattened to give it a little back pressure. Replace the exhaust manifold studs, they were two different sizes on it.
Why can't the head be milled. Is there not enough material to work with. I would love to get the compression to 10:1. Can it be milled just enough for a flat clean surface?
Where do I get the bigger exhaust valve? Can you put in a bigger intake to? Is the cam off of a atc 110 bigger then the atc 90 cam?
Where do I look to download the manual?
If I find a 22mm carb, does it have to be re jetted?
Where is the best place to get points and condenser? Does someone know the part #'s?
Thanks in advance for the help. I think the real world experience is far better then information. I did some research on the trike. I learn a little so far, but it will pail in comparison to the info i will learn here. Thank you to everyone.
Trevor.

[Mr_RPM]

i got myself a 56mm 10.5:1 compression for my 110 on ebay, maybe look for a piston a bit smaller on ebay. with the bigger carb im saying you will have to re-jet, just go by a bunch of diff sizes and start big and go down. for all the tune up parts and such, ebay has only been good to me. try there

[n10sivern]

Dratv.com has lots of parts for the atc90. They are great to deal with and ship fast. Also check out eBay.

[turbowrenchhead]

I have checked out Dratv.com. He quoted me $135 for cam, carb and 54mm piston. However he is out of cams for a few weeks. So will the 110 stock cam work?
I found the service manual and I'm printing it off.
How much of a bore can the stock cylinder take?

[Vealmonkey]

Okay, your next area of concentration is the points and condenser and setting the valves and timing. You will find a manual to download on this website to a pdf file, so yo will have to print out pages. Not sure if you have a credit card to buy parts online. If you do, there are lots of decent sites. DRATV.com is a nice site and they have alot of honda90/110 parts. Not sure what your budget is, but you don't want to run that busted exhaust too long. If you can't find a decent used exhaust, you may want to try a DG, you can still get them new. Most people don't like the cobra exhaust as they are too loud and obnoxious. I thought you could still get jardine exhaust too, but maybe I'm wrong. Once you get your points and condenser and timing straightened out, then you will want to adjust your clutch. It will be explained in the manual how to do it. One thing you didn't do, and you need a right side clutch cover gasket for this is, to clean out your oil screen. It's the closest thing you have to an oil filter on the 90 and it's inside the right clutch cover, that's why you need the gasket. If your oil was that dirty, than your oil screen is probably pretty crappy too. And the oil screen is what blocks crud from getting into your oil pump. So it's kind of critical to make sure it's clean. It sounds like your well on your way to get your trike running right and moving again. Until you have all your basic systems working, I wouldn't worry about too much trying to hop it up. That will all come soon enough. Keep up the good work. Hopefully your trike is rolling a little smoother now. Now onto making it run better.

[turbowrenchhead]

Will this carb work? It looks quite different from the 110 carbs that I have looked at on ebay.
I notice that it doesn't have an air mixture screw. Wouldn't you want one?
It also says that you have to operate the choke with a wire. Can that be eliminated? I looked at carbs for the 100's taking greenhumans advice. I have no idea witch carb to go with because of all the options that are out there. Too many choices.

http://cgi.ebay.com/ebaymotors/CARBU...Q5fAccessories

[greenhuman]

Here is the carb you want. Ebay 250587111834
You don't need to shave the head. It does not seal like it looks. When you get the head off you will see what I mean.
The inlet side of the manifold needs to be opened a bit for this carb but then it will bolt on and I have found the stock jetting in this carb works well with the 54mm piston kit.
Don't worry about a larger inlet valve. No advantage for this size engine. Just make sure you stock head is in good shape.

[turbowrenchhead]

I looked at that carb. Where is the choke on it? The seller has only one pic of the carb.
If I don't win that carb what would be an alternative? Is the 22mm carb on DrATV.com a good deal?

Vealmonkey. I checked out DG. Their exhaust is $149. Is there a cheaper alternative. I paid $145 for the trike.

Is this the gasket I need?
http://www.dratv.com/goilpu2.html

Greenhuman, where do I get the bigger exhaust valve?

[Vealmonkey]

As far as pipes, you can put whatever you want on it. There are cobras and they are cheaper and the majority of people hate them. I just gave you a suggestion from what I know and have done personally. You can just put a muffler from a lawnmower on there if you want, it's your trike. And that isn't the right gasket, buy yourself a gasket kit. You'll be doing yourself a favor in the long run instead of trying to get individual gaskets. A gasket kit should have an exhaust gasket in it too. Plus there should be new o rings for your valve covers for when you set your valve lash and timing. Like I keep trying to tell new people, cheap trikes cost money to get going right.

[Dirtcrasher]

Remember that your "fortunate" to get a cheap trike thats a piece of history.

Lots of guys can fab up exhausts but there is time involved in that too........

Be glad that you got it so cheap and that you can get a free manual here. How can ya beat it??!!

I agree, get it running, then worry about performance but it's certainly nice of greenhuman to suggest the upgrades many guys want/need..........

Get it running right, enjoy it a bit and then put it away and buy another trike , thats what we all do anyhow

[turbowrenchhead]

I will be getting the gasket kit. I have printed off the 38 page manual. I will be working on the trike tonight. Checking the points, condenser, setting the timing and valves. Checking the rear bearings.
I found a stock exhaust with the baffle removed.