Carb size

[shee4speed]

Well I tried to search but no luck. I was thinking of upgrading my carbs to match my port work and mods. (there in my sig.) So what would be the perfect size? I dune alot and hillshoot alot. Thanks!

[shanYE west]

I think 35pwk's would work well.

[BigRed350x]

Yeah, I'd say anything from a 33 to a 35 will be good for you. If you plan on doing more drags I'd go 35. If you dune more or play more I'd go with a 33. Keihin is my choice. I have both mikuni and keihin and prefer the keihin's.

[shee4speed]

would the 35's hurt the performance duning verse the 33's? would i see lots of seat of pants upgrading carbs.

[shanYE west]

would the 35's hurt the performance duning verse the 33's? would i see lots of seat of pants upgrading carbs.

 

You'll see better throttle response and bottom end with the 33's but the 35's will pull harder on top.

[Snopczynski]

You'll see better throttle response and bottom end with the 33's but the 35's will pull harder on top.

 

Screw all this, get rid of your sandstar paddle tires first.

[Bobman13]

Spoke to Kevin at herjugg and asked him a similer Question, His responce was that the 33 would retain the bottom end but would not provide a strong top end compared to the 35 he did recomend either the 34mm PJ or the 35mm PWK all around he said to go with the 35mm.

 

However I also talked to Cascade Inovation's They told Me that they recomended the 28mm PWK all around with the Dune Port on stock Cyclinder up to a .060 over bore regardless of stock or +4mil crank, and that he personally has never had good luck with the 33PWK. He did tell me that he would only suggest that you get the 35mm PWK's if you were going with a cheetah Cub setup and 4mill on Up.

 

Now Personally I have had excellent results with the 28MM PWK's and I had a Mild Dune Port stock Bore/crank and It worked flawlessly for me Never had Jetting issues at 5000 feet or at sea level I did rejet the maind ofcourse for the diff. alt. but it was pretty much set and forget.

 

Now I know that Duncan Racing National Kit has the options for the 35mm PWK but the use the 34mm PJ with Great results over the years and that motor was stock bore and Crank, But highly ported.

 

so the choice is yours!

[shee4speed]

Screw all this, get rid of your sandstar paddle tires first.

the sandstars are actually working well. I havent had a chance to compare them but once they are shot haulers are next. Thanks Snop. next season will be bigger carbs and haulers and maybe some more stuff :shrug:

[Snopczynski]

There is no way in hell you need 35mm carbs if your play riding and have a dune port. I would run a 28mm pwk's, or 32mm lectron's if you really want to put a big set of carbs on it.

[MDS2106]

I run 34mm pjs and love them.Big improvement over the stockers and the 30mm oko's that i was running.It took me a little fine tuning to get the idle right, but once I got that down it was cake.

Edited February 14, 2008 by MDS2106

[bigboybanshee]

I run 34mm pjs and love them.Big improvement over the stockers and the 30mm oko's that i was running.It took me a little fine tuning to get the idle right, but once I got that down it was cake.

 

That's exactly what I just put on my bike and I'm real happy with the performance gain. The bike has great response from bottom to top.

 

I was going to recommend what most people are suggesting, 33-35mm carbs, depending on if you drag or dune more often. You could always do what I did and go with some 34mm PJ's, right in the middle :biggrin:

[angler]

Well I tried to search but no luck. I was thinking of upgrading my carbs to match my port work and mods. (there in my sig.) So what would be the perfect size? I dune alot and hillshoot alot. Thanks!

 

 

I also have an aggressive dune/play port with stock carbs. it was all fine with FMF pipes but as soon as I put on the CPIs I ran out of gas in 4th gear (racing.) I was told that the bowls are too small on stockers. I can't imagine that 28s are going to hold much more gas than 26s? Everyone is telling me to go with 35s. You could always put those velocity accelerators in 35s for more bottom end. That's what I'm doing unless someone tells me something negative about those.

[Hilarious]

35 pwks all the way.

That is what I had on my duneport with +5 timing and shearers.

Had plenty of bottom, mid and top end.

 

Sorry to jack this thread but, how is kevin's duneport?

[Snopczynski]

Often times people dont use big enough fuel line, and or set the float level right. This can cause the bowls to go dry.

 

The things is this: Yes you put on a 35mm pwk, and it feels great. but if you would have bolted on a 28mm pwk or even a 33mm pwk you would have retained more bottom end power, and the top end would stay the same. Well why you ask? Because when your running a carb thats too big (like a set of pwk 35mm carbs on a dune ported motor) you will lose torque because of lower intake velocity, and only really pull max rpm the motor can acquire. The bottom end will suffer though. So you move down in mm, then you have better intake velocity which will make better bottom end, and your topend stays the same because you were over carbed in the first place. I know this much, the 2 into 1 35mm pwk on my bike was borderline too big, it showed signs of weird sign off power at peak rpm on the dyno that indicated it was almost too big. I find it hard to believe a ported 350 thats not a full blown drag bike needs anything much bigger than a 30-33mm set of twin carbs. Bigger is not always better.

[angler]

Often times people dont use big enough fuel line, and or set the float level right. This can cause the bowls to go dry.

 

The things is this: Yes you put on a 35mm pwk, and it feels great. but if you would have bolted on a 28mm pwk or even a 33mm pwk you would have retained more bottom end power, and the top end would stay the same. Well why you ask? Because when your running a carb thats too big (like a set of pwk 35mm carbs on a dune ported motor) you will lose torque because of lower intake velocity, and only really pull max rpm the motor can acquire. The bottom end will suffer though. So you move down in mm, then you have better intake velocity which will make better bottom end, and your topend stays the same because you were over carbed in the first place. I know this much, the 2 into 1 35mm pwk on my bike was borderline too big, it showed signs of weird sign off power at peak rpm on the dyno that indicated it was almost too big. I find it hard to believe a ported 350 thats not a full blown drag bike needs anything much bigger than a 30-33mm set of twin carbs. Bigger is not always better.

 

 

Do you think adding Velocity Accelerators to a bigger carb addresses both bottom end and top end issues?