Tim's ATC500R Decompression Mechanism - FINAL UPDATE!!

[atctim]

The slide is in pretty good shape - not worn too much. There is no airbox - just the rubber boot back to a sideways mounted filter. Should I try a different main?

[Louis Mielke]

I meant the literal shape, is it round, flat with curved sides, or is it shaped like a D. The main is up to you, depends on how your plug looked that kinda thing. I really wouldn't suspect the main for starting problems but I'm far from a jetting guru. Billy would have better jetting advice than me.

[cr480r]

The easiest way to tell the differences if you are not familiar with keihins is by the idle adjustment... the PWK have a idle screw, and the PJ's adjust idle speed with the choke

[Louis Mielke]

I have a 39mm PWK. 55 pilot, 172 main. I think I really need a 175. blah. Man I wish I was at home.

[Jason Hall]

Tim has a PJ carb on his 500. It Idles perfect with no trouble when Its running. I was going to adjust on It at the last Indoor race, but It needed nothing. I think he just needs to figure out what technique the engine wants to make it start.

[atctim]

Yeah - plug looks great after plug chop - it is a starting issue - and I think I do need to learn the technique, but I also believe that the reeds are playing a big part in that. They were really shot. I will know as soon as I get them in.

Thanks for the comments and info guys.

So when you guys are talking about PJ and PWK carbs - those are Keihin models then. I always thought PWK was a carb name brand. Show how little I know.

[Louis Mielke]

Tim have you tried adjusting the decompress so maybe it doesn't hold the vavle open so far? Maybe you're loosing a little too much compression? I would think you could adjust the cable so it just cracks the valve open when you're on the lever. I would think with cable adjustment you could adjust the speed of the compression being bled out.

I know it took me some fiddling until I found out how it worked best.

Jason what do you think of this idea? I know you're really experienced here too.

PWK, PJ, PE are all types of Keihin carbs Tim.

[atctim]

didn't think of that Lou - I will try that.

But not until I get it all back together again. Will be at least a week. waiting on reeds - need to modify my brake lever now, kicker hits it - I have to get the shifter fixed too.

Will let you all know when I know.

[Louis Mielke]

Will you have it for these weekend do you think?

[Jason Hall]

I think If the reeds are hanging open and the compression release Is opening to much, It's possable he Is bleeding off to much compression. Did you try flipping the reed pedals Tim, or are they just totally hit?

[atctim]

Jason - the reeds are Tostidoed! no good on the flip.

Lou - I'll be running the 86R this weekend - no way the 500 will be ready.

[Billy Golightly]

I was just curious on the carb, I ran the PJ on mine for 2 years in a row at TF, and once it was dialed in it ran very well. The 39 or 41mm Taperbore PWK carbs are even better, there a little bit more forgiving on the jetting and when you do get it to sweet spot good christ does whatever its hooked to run good

My 500, for the most part had a trick to it, I think all of them do when their dialed right. I always when I kick it, use the tip of my boot, out right behind my toes, and I "flick" the kick starter, which allows the motor to turn quicker and I always do it as the motor is coming UP on TDC, where the compression is building. I'd try it 3-4 times with the choke on if it was cold, and if that didn't work I turned the choke off and held it wide open, and normally within 5-6 "flicks" of the kicker it would start and scare the bejesus out of ya when it did.

[FPMXer]

This should help with kicking over the hundy motor.

http://media.putfile.com/Crankin-up

[Louis Mielke]

Thanks for the vid but you're missing one small detail. We're using a shorty yamaha blaster kicker to clear the fenders better on our bikes.

[atctim]

Your bike is an 1989 - my engine is a 1985 <no scallops

Big difference in kicking them over. People that don't have these conversions and older style engines must have it pretty easy!

As Lou stated - I did not put this compression release in to make it easier to kick over - I could kick it over just fine. Also - in your video - you say "gas on, no choke" - does that apply to me? It looks nice and sunny in that video - leaves are on trees........it is 5 degrees Fahrenheit here.