I have been here a long time, and I know there are lots of posts on this. I have screened almost all of them in the last few months since my rebuild.

I am currently running a ct full pipe, prodesign k&n factory box w/o lid, wiseco 11:1 100mm piston and stage 1 hc. Using mikuni jets, I have 25 needles and 175/180 mains, running about 3 turns out on the screws. Temperature is around 40 deg, elevation is a couple hundred feet about sea level. Carbs are stock.

I have been constantly overheating, I have poor throttle response, I do not notice any backfiring on decelleration, I have noticed a lack of power pretty much everywhere. It has been threatened in a drag by my cousin's bone stock 02. It no longer wheelies like it did when stock. I have checked the coolant and it has been holding both in the radiator and the resiviour. I have played with the idle screws. I thought I was too lean, but I look here and see that people are running 180/185 setups in their 686's with stage 2 cams. Plug is very inconsistent. Sometimes I am lean, sometimes I cant tell, sometimes it looks fine. All seals, bolts, installs, etc have been checked and double checked. Valves have been set at just under hc specs. Timing is on, cam, piston, and rings installed correctly and broken in. It still runs like crap. Any suggestions?

 

You could be loosing some compression. If your bike is overheating this can cause lots of problems it could of gotten to a point where the piston actually gets tacky and almost siezes but if you keep the bike running it will just screw things up and not actually weld together...that could be where you might be loosing power and compression. Try pulling off the top end and checking everything out.

 

My first question is why do you think its over heating?

I don't really have much to offer right now. Thats a pretty general problem, kind of. I would say jet up and set the valves to hot cams specs. To tight of valves can cause problems like you are talking about, but normally other problems arise first. And of course being lean will over heat it and cause poor performance problems. If you do try that do them one at a time so you will know which one it is.

I was running 170/175 with no interanl mods and clamp-on filters when it was 80+ degrees.


How about an air leak? That would also explain the inconsistant plug readings (I hate pug readings anyway).

 

Are you running stock valves? A friend of mine also ran a little lean sometimes and when we tore it down we found the valves were beat to hell. Loosing compression through there. Also what type of fuel are you running?

 

I'm running 93/94 octane, depending on where I fill up. I was running 170/175 with the 25 needle with the K&N and pipe, no lid. I am going to rejet to 185/190 and move back to 3rd clip this weekend. Is it possible that I would be losing compression at the cam tensioner fitting? That gasket was replaced the first time the engine was torn down, but may not have been the last time. I tore down the head a few weeks ago (havent done more than 10 mins riding for tuning since) and the piston looked pristine, with just a little bit of black on it. Rings seemed to have sealed well also. I am running stock valves and springs with the stg 1 hc. The reason I have them a little tighter is because the others on this forum have suggested lash specs much tighter than hc, but still larger than stock. Valves look fine and they can scarcely be heard over the engine at idle. I will be doing a compression test this weekend as well.

How many psi should I be registering with the 11:1 stock bore?

 

Track down Sixsixt he is great with jetting. I think you are lean with how cold it is.

 

No

I wouldn't jump up that much on the jets. Just go up one size in each carb and see if it helps. If you start doing a bunch at one time it can be hard to tell what helped or hurt.


Have you noticed the cap popped of the coolant ressy? Or any bubbles blowing in it while your running, paticularly while on the throttle? ......I know its tough to see with the throttle gapped back.[img]i/expressions/face-icon-small-wink.gif[/img]lol


I don't know about how many psi it should have. I was actually wonderring what I should have.?.?