carbs?

[twinzr900]

ok i am getting the 4mm stroker and the 5mm long rods and the porting done. i dont really have the money to get the bigger carbs right now. would it just be a waste of money to try and run them through my stock carbs or no? also would i need to advance my timing at all? this is just gonna be my trail bike w/ some pavement streches.

[white trash]

It wont hurt the motor at all running stock carbs, but it will hinder the performance. To get the max out of it you should look into some 35 mm carbs

[odaen]

It wont hurt the motor at all running stock carbs, but it will hinder the performance. To get the max out of it you should look into some 35 mm carbs

363883[/snapback]

 

I think there are some common misconceptions about carbs and performance from what I've seen. I have a 4mm motor with 5mm long rod that has a good dune port from Redline. I run stock carbs that have been bored some, and they will develop more peak HP than 28pwk's or 35mm's. Bigger carbs can give you more low-end torque and HP, but you will sacrifice it on the top end. One explanation that made sense to me, was it was a trade-off between volume and velocity. So, it's kind of a trade-off. I've seen numerous dyno sheets with motors identical to mine at my builder's shop, where the only thing different are the carbs and it fits what I said.

[dajogejr]

I'd see how much someone reputable can bore you stock carbs out to 28mm.

 

I'm sure someone on these boards can either reccommend a good tuner...or might even do it themself.

 

That should fix your itch for a while...and be much, much easier on the wallet...

[1800bigk]

I think there are some common misconceptions about carbs and performance from what I've seen.  I have a 4mm motor with 5mm long rod that has a good dune port from Redline.  I run stock carbs that have been bored some, and they will develop more peak HP than 28pwk's or 35mm's.  Bigger carbs can give you more low-end torque and HP, but you will sacrifice it on the top end.  One explanation that made sense to me, was it was a trade-off between volume and velocity.  So, it's kind of a trade-off.  I've seen numerous dyno sheets with motors identical to mine at my builder's shop, where the only thing different are the carbs and it fits what I said.

363912[/snapback]

 

 

so let me get this straight, bigger carbs give more low end and sacrifice top end performance while smaller carbs give more top end performance and less low end than the bigger carbs.

[odaen]

so let me get this straight, bigger carbs give more low end and sacrifice top end performance while smaller carbs give more top end performance and less low end than the bigger carbs.

363953[/snapback]

as a blanket statement, that might be a dangerous statement. his motor sounds close to mine, in terms of the 4mm and dune port. volume isn't the only thing to consider.

[twinzr900]

so do u have to do anything w/ your timing or no? i was thinking about the adjustbale timing plate.

 

 

this may sound stupid but i am just curious. do you HAVE to get a port job done to run this set up? (yes i am doing it anyway) but was wondering if you even had to.?

[dajogejr]

Have to? Nope.

 

With the extra cc's and money you're putting into it...it sure would be a waste not to...

 

Be almost the same as getting a stroker and bore kit, and leaving the stock rear tires on.

 

Ok...well...almost, but you get the point.

 

[decon]

I think there are some common misconceptions about carbs and performance from what I've seen.  I have a 4mm motor with 5mm long rod that has a good dune port from Redline.  I run stock carbs that have been bored some, and they will develop more peak HP than 28pwk's or 35mm's.  Bigger carbs can give you more low-end torque and HP, but you will sacrifice it on the top end.  One explanation that made sense to me, was it was a trade-off between volume and velocity.  So, it's kind of a trade-off.  I've seen numerous dyno sheets with motors identical to mine at my builder's shop, where the only thing different are the carbs and it fits what I said.

363912[/snapback]

 

got dynos? from my knowledge u need bigger carbs on a stroker, not smaller ones. all the people on here with strokers will say that bigger carbs are your ticket. i would say get either some 34 or 35mm carbs. you can run small carbs but you wont get the full potential out of your motor. just run the stock carbs and save up some cash for bigger ones.

[stclark816]

You are gonna gain more outta ur stroker with bigger carbs. Ive never heard of anyone putting smaller carbs on their stroker motor. Doesnt make since to me, but oh well. I run 33mm PWK's on my 4mm. Bike dynoed at 85 HP on gas. I would imagine if I put stock carbs on my bike, it would hinder the performance.

[Ducman]

I think there are some common misconceptions about carbs and performance from what I've seen.  I have a 4mm motor with 5mm long rod that has a good dune port from Redline.  I run stock carbs that have been bored some, and they will develop more peak HP than 28pwk's or 35mm's.  Bigger carbs can give you more low-end torque and HP, but you will sacrifice it on the top end.  One explanation that made sense to me, was it was a trade-off between volume and velocity.  So, it's kind of a trade-off.  I've seen numerous dyno sheets with motors identical to mine at my builder's shop, where the only thing different are the carbs and it fits what I said.

363912[/snapback]

 

 

So If I want to get the maximum HP out of my 4mm motor, according to your accurate conceptions about carbs, allong your line of reasoning I should look into getting some duel 20mm carbs? How about you and I race 100 yards on foot while you suck air through one of those pinner coffee stirr stick straws and I'll use a big ol' Mac Donalds straws. I can see how some settups might make bigger HP dyno #'s on small carbs but not a typical 4mm motor, especially like a dune port.

 

I'd say stock carbs would be fine on a mild trail port 4mm motor, if you want something more like a dune or drag port that will make a lot of HP then get some duel 34mm carbs.

[BdBanshee]

You are gonna gain more outta ur stroker with bigger carbs. Ive never heard of anyone putting smaller carbs on their stroker motor. Doesnt make since to me, but oh well. I run 33mm PWK's on my 4mm. Bike dynoed at 85 HP on gas. I would imagine if I put stock carbs on my bike, it would hinder the performance.

364070[/snapback]

 

Exactly what he said.

 

Big carbs have more top end on modified motors, and many times the larger carbs will also have as much low end as a stock carb. Stock carbs will have more low end on stock or mildly modified motors.

[superchicken]

bigger carbs= higher velocity at higher rpms= more top end hp

 

smaller carb=higher velocity at lower rpms= more low end

 

you dont put a 600 cfm on a 454 big block you put on a high rise intake with duel 750's to get it going were its gonna make the most power in the upper rpms

[locogato11283]

I think there are some common misconceptions about carbs and performance from what I've seen.  I have a 4mm motor with 5mm long rod that has a good dune port from Redline.  I run stock carbs that have been bored some, and they will develop more peak HP than 28pwk's or 35mm's.  Bigger carbs can give you more low-end torque and HP, but you will sacrifice it on the top end.  One explanation that made sense to me, was it was a trade-off between volume and velocity.  So, it's kind of a trade-off.  I've seen numerous dyno sheets with motors identical to mine at my builder's shop, where the only thing different are the carbs and it fits what I said.

363912[/snapback]

i think you have that backwards. if smaller carbs gave you more on top youd have every engine builder runnin stock carbs on their 10mm strokers. it just doesnt happen. bigger carbs = more on top. in fact, with a 4mm stroker its possible to drain the float bowls if you are WOT for a long time. 4mm suck a lot more gas than a stock motor will. on a 4mm stroker i would recommend no longer than 33mm pwk's.

[odaen]

holy crap, everybody came out of the woodwork for this one. I think that people are overgeneralizing what i said. I never said a pair of 20mm carbs was gonna pull more peak horsepower out of a 4mm motor. I said there was a trade off between volume and velocity. when someone that knows as much shit about banshee motors as the guy that built mine tells you that he doesn't put anything over a 30mm's running pump gas on a 4mm stroker, and shows you plot after plot of bikes that he's built, at some point, you just have to come to a point where he knows what the hell he's talking about. he told me within 1 hp what my bike would dyno at before he even finished assembling it. Many people told me it wasn't possible and that he was 7-10hp too high on his estimate. so, I guess what I'm saying, is run what you want. I'll be the moron with the 26mm carbs pulling 76HP with pump gas.

 

and for the physics guy who posted about velocity and volume

 

take a garden hose with no nozzle and turn the water on. what's the velocity of the water compared to partially covering the end of the hose with your thumb. it doesn't matter how hard you turn the water on at the valve, holding your thumb over part of the end will always produce an increase in velocity.

 

honestly, i got thick skin, so flame on if you feel the need. i wasn't trying to be a dick when i first posted this, i was just passing on information that had been passed on to me in the hopes of saving someone some $$

Edited May 4, 2005 by odaen