CR 500 pwk question

[uts]

Hey there, I have heard good things about changing from a pj to a pwk carb for my cr500. I have found a pwk but it has been bored out to 41mm (kart racing). Question is pros and cons of this and what jetting specs to START with as to not risk engine damage when I throw the pwk in. I am guessing richer jetting, but how much ish?
UTS

 

[plynn41]

The PWK will be easier to jet and give smoother overall response than the PJ. The 41mm is pretty big if you are doing single track or MX. The bike will probably loose some low end grunt. I've got a 40mm PWK on my CR500 and like it.

As far as jetting, I'd start with stock. When I put the PWK on my bike, it had the stock KX500 jetting for the bike the carburetor originally came from. The bike started on the first kick (seriously) and instantly idled, so I knew the pilot was close. BTW, there is alot of jetting information on www.cr500riders.com and www.bannedcr500riders.com that you could take advantage of.

 

[whenfoxforks-ruled]

As long as you do not run the bike for long periods, jetting lean will not kill your engine. Didn't that come with a 38? Are you going to use the engine in a cart? Vintage Bob

 

[uts]

No no, it came from a kart vintage bob, that's why it is bored soo much. Thanks guys

 

[whenfoxforks-ruled]

Unless you are using this for extended WFO conditions, I would be looking for a smaller carb. The bike lacks a workable bottom end, no power valve. My 480 is seriously useless in first gear, with stock gearing. I am going the complete opposite direction, confident the motor can pull it easy. The carb just needs to run clean off bottom, and stretch the top. The 38 pwks are cheap and plentiful.

 

[helio lucas]

Unless you are using this for extended WFO conditions, I would be looking for a smaller carb. The bike lacks a workable bottom end, no power valve. My 480 is seriously useless in first gear, with stock gearing. I am going the complete opposite direction, confident the motor can pull it easy. The carb just needs to run clean off bottom, and stretch the top. The 38 pwks are cheap and plentiful.

VB is the man!!!

for normal use (enduro, mx etc) you want a carb that cleans the bottom and the transitions not a top end moster. for some reason a 500cc have more or less the same carb as a 125cc. :nod:

 

[plynn41]

Seriously uts, check out one of the CR500 forums.

 

[whenfoxforks-ruled]

Ask AJ. Nobody knows how to tune a CR500 better. Do they come with a 41?

 

[Lorin]

I ran a 40mm pwk on my wr500 (no power valve) and didnt lose any low end on my part. I was able to jet fairly sharp and was happy with the swap.

 

[whenfoxforks-ruled]

I know a guy swears up and down, you have to drill the petcocks out on big bore bikes. When that sucker runs lean, I will check that? Starving fuel would be a major concern, and make for dangerous situations.

 

[uts]

Thanks guys

UTS

 

[uts]

VB is the man!!!

for normal use (enduro, mx etc) you want a carb that cleans the bottom and the transitions not a top end moster. for some reason a 500cc have more or less the same carb as a 125cc. :nod:

Hey just thought I would mention that down here i Aus VB is a really crap beer! Don't take it that association Vintage BoB!!! :nod: