Best carb option for CR500

[tdorval]

I just picked up an 88 CR500, still debating on just putting forks on it or doing an AF swap to a gen 3 250. Anyway, I'm going to have a decomp installed in the head, rebuild the top end, inspect the bottom end and rebuild if needed. What I'm unsure of is what carb setup to run. So lets here some experiences on the different carbs (Lectron, Smart Carb, Pulse injection, 38mm airstryker, 39pwk etc) and pro's and con's. This is obviously for a snowbike application so something easy to tune and forgiving would be great. Will be riding mostly in Colorado, 9-12'k+ in varying temperatures. I know this is a hot topic but I haven't seen all the info in one location yet. Cost is also a concern as I noticed some vary in price quite a bit. Thanks and I look forward to all the feedback.

 

[portgrinder]

lectron 44 gained me 4-5 hp all the way thru the rpm range on my kx500. real happy with it. adjusted from the parking lot -10C up to 6000ft and +2C with not an issue.

they are great guys to deal with. no i did not get a deal, paid regular price like everyone else.

 

[tdorval]

PG- Does the lectron run well through out the entire rpm range? I've read where people say its more of an all or nothing carb thats hard to tune for anything but full throttle. How is the throttle response on the 44? Any fitment issues with the larger carb?

Thanks for the info so far!

 

[egesledder]

A stock 39.5 PWK from a later model KX500 would be a good cheap upgrade over the stock 38 PJ carb on the CR. I just picked up a Lectron 44 high velocity carb for my KX500, but I haven't had a chance to ride with it yet. I need to get a carb heater for it first.

 

[wwillf01]

PG- Does the lectron run well through out the entire rpm range? I've read where people say its more of an all or nothing carb thats hard to tune for anything but full throttle. How is the throttle response on the 44? Any fitment issues with the larger carb?

Thanks for the info so far!

I find as you go up in the size on the lecterns or any meter carb it becomes more all or nothing loosing some lower end grunt.... That's a big arse carb.....


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[SEOINAGE]

I've heard good things about the pwk 39mm. I'm planning to order one up this week.

 

[portgrinder]

i had a bored pwk before, so like 40.5.

it runs pretty good everywhere. i'm a little lean at high rpm, low throttle so i'm going to go up a little on the rod. should be no big deal.

also noticed you dont need a primer. used a primer on my pwk. tried my old method of a couple squirts and thats way too much fuel. with the lectron its pull the choke, roll it over a few times and within half a dozen kicks or so its running. this is at -15C

edit: 44 might be a little big on a stock motor. maybe a 44hv, 42, 40 ect...

 

[summitboy]

I run Pulse Injected PWK 38. It will flow more air than a 40mm according to Ron. You can tune the entire fuel circuit with the air screw. It is also deals eith the altitude much better than a stock PWK. Runs excellent, idles excellent and dead easy to jet. I have only changed the main/pilot jet once on my first ride out last season. I had Ron open up my choke circuit when he did the Pulse mod and it starts very easy. It also run smoother than a stock pwk and the Smartcarb i had.

 

[tdorval]

Some great feedback so far guys. I like the idea of how the pulsed setup is forgiving to elevation changes and if you do need to make changes its just with the aircrew, simple. Just wish it wasn't $700 for the setup, I guess I could do it in stages as funding allows. How are adjustments made on the lectron? Summitboy, do you think opening the choke circuit helped more with cold starts or does it have more to do with the actual pulse deal? Keep the info rolling guys.

 

[SEOINAGE]

I run Pulse Injected PWK 38. It will flow more air than a 40mm according to Ron. You can tune the entire fuel circuit with the air screw. It is also deals eith the altitude much better than a stock PWK. Runs excellent, idles excellent and dead easy to jet. I have only changed the main/pilot jet once on my first ride out last season. I had Ron open up my choke circuit when he did the Pulse mod and it starts very easy. It also run smoother than a stock pwk and the Smartcarb i had.

Can't you do this without it being pulsed?

 

[egesledder]

I ran the stock 39.5 PWK on my KX500 with a 525 big bore all season last year in Colorado. Once I had the jetting dialed after the first couple rides, I didn't touch it for the rest of the season. That was riding everywhere from 8500' and up to probably 12k at most. It rips pretty well and I probably should keep running it because it just flat works, but I wanted to try the Lectron to see if it makes more power on the top end.

Keep that in mind though before you go spending big money on a carb that "compensates" for altitude, the pwk does pretty decent for the riding in Colorado.

 

[SEOINAGE]

I ran the stock 39.5 PWK on my KX500 with a 525 big bore all season last year in Colorado. Once I had the jetting dialed after the first couple rides, I didn't touch it for the rest of the season. That was riding everywhere from 8500' and up to probably 12k at most. It rips pretty well and I probably should keep running it because it just flat works, but I wanted to try the Lectron to see if it makes more power on the top end.

Keep that in mind though before you go spending big money on a carb that "compensates" for altitude, the pwk does pretty decent for the riding in Colorado.

Good to hear. I think we sometimes forget that as it gets colder it runs leaner, and that can compensate for an increase in altitude as well. I could likely jet my bike the same for 4000 ft and 65 degrees, as 10000ft and 25 degrees.

The issue I am having with my PJ is after I've ridden it a bit and I do a climb or ride around a bit on the throttle, when I come off the throttle it sounds like it is starving for fuel, running lean, but then drops back down. I don't think I have a fuel flow issue, but I could take off my spill valve and see if that is the cause. I was also told this carb is impossible to get just right. I'm overall running a little rich during break in, and will make adjustments from there after a couple more hours of engine time.

 

[egesledder]

Is this on the snow? If so, are you running a carb heater? It could be slightly icing around the venturis, causing it to run lean. If not, you could try going up one size on the pilot and seeing what happens, or adjust the air screw a bit and see if it makes a difference.

 

[SEOINAGE]

Is this on the snow? If so, are you running a carb heater? It could be slightly icing around the venturis, causing it to run lean. If not, you could try going up one size on the pilot and seeing what happens, or adjust the air screw a bit and see if it makes a difference.

No snow, but it is cold. I actually think I'm about right on on the pilot, as it runs fast at about 2 turns out, might need to be one step leaner though. I've messed around with it a bit, and I can be rich everywhere else, but still come back to idle and start starving for a good 5-10 seconds.

 

[tdorval]

Do any of the carbs start back up after a roll over better then others? I guess that's if you roll a bike haven't been around them enough to know what's normal for these things. Egesledder how did your pwk start when cold last season?

I didn't realize how many CO folks were on here. Hopefully I run into some of you guys!

 

[M5-]

Your motor is basically the same as mine. If you are tight on cash I would buy a new 38 PWK Airstryker, which is what I have, jet it and run it as is. It will run great, its easy to start after a roll over and starts cold no problem. By going this route you will already have the correct carb to pulse at a later date when you have the money and in the mean time the bike will still run great. Regardless of what you decide to go with carb heat is mandatory.

M5

 

[tdorval]

I'm considering that as a good option. I am planning on using a heater with whatever I go with.

 

[SEOINAGE]

Your motor is basically the same as mine. If you are tight on cash I would buy a new 38 PWK Airstryker, which is what I have, jet it and run it as is. It will run great, its easy to start after a roll over and starts cold no problem. By going this route you will already have the correct carb to pulse at a later date when you have the money and in the mean time the bike will still run great. Regardless of what you decide to go with carb heat is mandatory.

M5

Why airstryker over the 39mm pwk? I know this has been talked about before, but I thought there was little benefit to the airstryker if any over the 39.

 

[NUSS]

Do any of the carbs start back up after a roll over better then others? I guess that's if you roll a bike haven't been around them enough to know what's normal for these things. Egesledder how did your pwk start when cold last season?

I didn't realize how many CO folks were on here. Hopefully I run into some of you guys!

I'm also running a KX500 with the stock PWK carb. After a roll over I just clear it out with a full throttle kick or two. It always starts right up.

There was only one day that I had a problem starting it in the cold but I also don't have a primer. I ended up tipping the bike on it's side until fuel was pouring out of the vents and it started up just fine.

To add on jetting. Once I had it dialed in, I didn't change the jetting at all throughout the entire season. I confirmed jetting with both EGT and AFR gauges. The bike just rips.

 

[wwillf01]

I ran the stock 39.5 PWK on my KX500 with a 525 big bore all season last year in Colorado. Once I had the jetting dialed after the first couple rides, I didn't touch it for the rest of the season. That was riding everywhere from 8500' and up to probably 12k at most. It rips pretty well and I probably should keep running it because it just flat works, but I wanted to try the Lectron to see if it makes more power on the top end.

Keep that in mind though before you go spending big money on a carb that "compensates" for altitude, the pwk does pretty decent for the riding in Colorado.

I would talk to Lectron but on my sons kx65 I gained 1500 rpm on the top... It will make difference on the top for sure. But if you have something that works why mess with it .. Just ride!


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