85 200x, .50mm 12:1 Wiesco. need carb adjustment?

[CanadianThomas]

Well. I was searching and searching last night for hours and while I think I am close, I couldn't find quite the info I needed so here we go.

Just bought a 85 200x, runs fine if the choke is on just a bit (using a piece of duct tape). Otherwise it bogs of the line. It also seems to hesitate or simply give out and gain no more power in the top end and it feels like it should have more. In going threw the repair book I got with it I found receipts from work done on it last year. He had it bored .50mm over and threw in a 4289P2 Wiesco piston, after looking up this piston I have discovered it is a 12:1 compression piston. Now I know why it is very hard to kick! I know this trike has almost no hours on it after it's rebuild as his son didn't like it. Loves MX?

So. I'm thinking that the loss of top end power is simply not enough octane in the fuel, I am running premium (91 where I live) but everything I read says I need to run 100 Octane with a 12:1 piston. So easy fix, get boosters.

But for the running with a little choke to get it running right. Could that be a jetting, or needle adjustment problem from the bore and comp of new piston? Bring the needle clip down a notch, maybe 2? I read here last night that the 85 200x has stock jet sizes of 38 and 108, when purchasing this trike I was given a little bag of tools, inside I found a carb kit for a 83-85 200x with 40 and 110 jets in it. Did he maybe forget to rejet after the piston?

Any advice would be great. Thanks.

Thomas.

[Dirtcrasher]

You DO need higher octane with 12:1 and depending on the cam, you may not get much low end out of it. Mine screams at high RPM's but it isn't so happy down low.

I'm too busy with my 350X build #2 that I honestly haven't put 60 hours on my 86 200X in 3 years. They are both 200X's, so don't let the year influence you.......

Someday I'll get it straightened out but that may mean going back to 10.25:1 and a mid-top range cam instead of a full race cam..... I'm tired of paying 50$ for 5 gallons of race gas only to let it go bad. The ethanol doesn't help if you run pump gas or a mix.

If it runs better with the choke, it needs a larger pilot, maybe the needle up a notch and a good look at the WOT plug chops.

I'll say this, jetting anything like this is an arduous task at least. You have to do one change at a time and record them in a diary. And temperature plays a HUGE roll in jetting......

It does keep up with my 350X though and the 350X has a 14 tooth front sprocket so that just shouldn't happen :lol: Almost feels like I have a "power band".....

[swifty]

jetting will be the least of your worry when you break the kicker shaft and have to completly tear the engine down i broke mine in 2 weeks with the 10.25-1 piston 85-85 have a horrible weak kicker shaft-gear setup id say 85% of 83-85 stock 200x have kickers that slip when you kick them but maybe you will be lucky.....ive had atc's that have been slightly out of time and would only run with the choke even with a clean properly jetted carb, just a thought

[CanadianThomas]

jetting will be the least of your worry when you break the kicker shaft and have to completly tear the engine down i broke mine in 2 weeks with the 10.25-1 piston 85-85 have a horrible weak kicker shaft-gear setup id say 85% of 83-85 stock 200x have kickers that slip when you kick them but maybe you will be lucky.....ive had atc's that have been slightly out of time and would only run with the choke even with a clean properly jetted carb, just a thought

When you say they slip, would that be like the kicker going loose and going down easy with no resistance or starting ability? If so I am safe for now. This thing is a monster to kick, doesn't always start on the first kick but it's always hard to kick.