What size carbs?

[gregrob]

Ok, I've decided on the Keihin PWK series carbs. Now I'm just trying to locate a good deal on a set and some intakes.

 

 

You guys think I should go with 33's or 35's?

 

My goal is to run these carbs on my ported stock stroke motor for now, and go to a 4mil crank eventually, so I only want to buy one set of carbs.

 

 

I know the bigger the carb your bottom end will suffer slightly, but will 35's make more power on top than 33's?

 

I'm up here at high elevation where I need to flow a lot of air so I'm thinkin 35's would work, just don't want it to be a dog.

 

 

If I go 33's can I have them bored when I go to a 4mil? How much can they be bored?

 

 

Thanks

 

Greg

[Screaming Yellow Zonker]

I would go with the 33's. The only thing you will have to do after the 4mm is change jets.

I am currently running stock carbs on my 4mm. But I have a set of 34's that I have to install.

[theshee]

Get the 33s bro... 35s would be a bit too much for your motor up here at our elevations. The 33s will also work fine with a 4 mil once you get it thown in there, will make one nasty hill bike for sure. Hit up Jeff and see what his price is, when I got mine he had the best price by far.

[fun_on_the_sand]

I would go with 35's, from what I read in your signature you have 19cc domes which gives you very good acceleration and dune porting (bottom to mid range), so that would make up anything the 35 carbs are taking away on the bottom range.

 

I have similar setup, 18cc domes, dune porting and advanced timming, and I just got the 39 PWK single carb set up on a trade where I was really looking for 2 PWK 35 airstrikers. I love my current setup, I do a lot of dunning and I'm never embarrased dragging on the hills.

 

Bottom line:

- Yes 35 carbs will give you better top end by making the bottom end suffer.

- You have other mods (19cc domes, dune port job, advanced timming) that helps your bottom end

- If you have stock carbs 26, there is not that much difference between 33 or 35, is it?

 

go for the PWK 35 Airstrikers!!! :thumbsup:

[jayzx10r]

I think my 33 PWKs are the perfect carb for my application...I have a 4mil/dune port motor and I run at sea level in the sand.

 

I'm not sure what your elevation or intended riding application is, but if you are at such a high altitude that you have to take it into consideration it in your design, I'd think a smaller carb would be better for you.

 

I'd think the 35 wouldn't even be on your radar and the 33 would be the biggest to consider. Maybe the 30 would be best??

 

In answering your question, carb sizing is a balance of factors...so if your question is:

 

What carb gives the most top end...that would be a 40mm. You obviously wouldn't choose it because it wouldn't atomize fuel at partial throttle opening so you wouldn't choose it.

I'm using is as an extreme example.

 

If you wanted the best throttle response for trail riding, smaller carbs would be the best choice because they mix air/fuel best at partial throttle positions.

 

Maybe your choices should be more in the 30-33mm range if you are at high altitude, otherwise you may give up a bunch of throttle response to gain a sliver of improvement in the wide open position...i'm leaning more toward the 30mm.

 

A lot of people make the mistake of running carbs that are too big and they end up getting motored by someone with a better carb choice.

 

Biggest isn't always best.... :thumbsup:

Edited March 26, 2008 by jayzx750

[Broke_Banshee]

I think my 33 PWKs are the perfect carb for my application...I have a 4mil/dune port motor and I run at sea level in the sand.

 

I'm not sure what your elevation or intended riding application is, but if you are at such a high altitude that you have to take it into consideration it in your design, I'd think a smaller carb would be better for you.

 

I'd think the 35 wouldn't even be on your radar and the 33 would be the biggest to consider. Maybe the 30 would be best??

 

In answering your question, carb sizing is a balance of factors...so if your question is:

 

What carb gives the most top end...that would be a 40mm. You obviously wouldn't choose it because it wouldn't atomize fuel at partial throttle opening so you wouldn't choose it.

I'm using is as an extreme example.

 

If you wanted the best throttle response for trail riding, smaller carbs would be the best choice because they mix air/fuel best at partial throttle positions.

 

Maybe your choices should be more in the 30-33mm range if you are at high altitude, otherwise you may give up a bunch of throttle response to gain a sliver of improvement in the wide open position...i'm leaning more toward the 30mm.

 

A lot of people make the mistake of running carbs that are too big and they end up getting motored by someone with a better carb choice.

 

Biggest isn't always best.... :thumbsup:

 

 

True bigger isnt always best,i have a trail bike with a modded motor but stock carbs and it walks over many,crazy

[shudakeptquiet]

True bigger isnt always best,i have a trail bike with a modded motor but stock carbs and it walks over many,crazy

 

 

I have 28MM and I love them

[jbooker82]

I would run the PWK 33's I run them on my Patriot Racing Drag Ported 4 mill stock cylinder motor at 2000 ft. They run great. Better throttle responce than my 34mmPJ's I use to have.

 

For an Intake there is only one way to go. Boss Racing or White Kunckle. They are a one pice intake and have a crossover tube machined in. They also move the carbs up and back so the LH Float Bowl doenst hit on the clutch arm. So there is no external tube. They also use standard mikuni carb boots that can be bought from dennis kirk for 12-15 bucks a piece.

 

[Animalman294]

Ya, those are nice intakes................

[jayzx10r]

Those are some puurdy intakes, bbooouuuyyy... :yelrotflmao:

[gregrob]

Thanks for all the input guys.

 

 

Just to clarify, yes I am at very high elevation compared to most. I live at 6,000 ft, and my two sand riding spots are 7,000 and 8,000+ ft.

 

So that definitely plays into the carb choice.

 

 

Looks like 33's are the ticket. If I found a screamin deal on a set of 32 or 34 Mikuni TM's I'd take them too, but I'm thinkin the 33pwk is right in the middle and from everyone I've talked to they are great carbs.

 

 

Keep it comin'

 

Greg