lets talk carbs motor set ups... size where do they help

[woodsracer144]

ok... i am left thinking and i dont get it...

for low end how does a 35 or a 36 mm carb help you get more low end? wouldnt a larger carb allow more air allowing more gas as well and then in return allowing more power? i'm looking for a goos solid low end set up for the woods but im running a 38 PWK right now..

also how much does the high compression help you in a 2 stroke over a 4 stroke...

all the dynos' i've seen are on 4 strokes that were tested and the result was that you gained very very little at the most like 7Hp.

so is it the same with the 2 strokes?

[kouki]

When you are talking about a small displacement engine such as a 250cc 450cc etc, 7 hp is a pretty good gain. As for smaller carbs for low end and larger carbs for top. Well on top end in the high rpms your piston is moving faster, so the larger carb is less restrictive allowing more efficiency when pulling in a high volume of air, allowing more power in higher rpm. In lower rpm, with a larger carb you are not making full use of the volume that carb is flowing, and that is in effect restricting your performance.

[woodsracer144]

How much hp is gained on 2 stroke motor with race gas ?

[1promodfan]

Originally posted by woodsracer144
How much hp is gained on 2 stroke motor with race gas ?

I'm not sure of the HP gain, but by running a race gas dome, you'll have more compression. More compression will give your bike a little bit more low-end grunt. I'm thinking of changing domes just for that reason.

[woodsracer144]

what do you think of running E85 in a RACE motor meaning high comperssion and all that... theres people on here running it on there 400ex with 13-1 and 12-1 pistons... for those who dont know its like a 105 or a 115...

[wilkin250r]

Smaller carburetors have higher intake velocity. This is obvious, if you're running at 3500rpm, the air will have to flow FASTER through a 36mm than it will through a 38mm, but it's not really "restrictive" yet at such low rpms.

That higher airspeed is the key. It gives you better throttle response, more accurate fuel metering, and better atomization of fuel for a better, faster burn.

Think about it. If bigger carbs were always better, than wouldn't we all be running around with 80mm carbs on our quads? Smaller carbs are restrictive at high RPMS, so obviously larger carbs perform better because they flow more. But at low rpms, when you're not flowing enough air to cause any real restriction problems, smaller carbs perform better.

[woodsracer144]

so what size is a stock carb? whats the best 36 or 35? make like just a pwk?

[1promodfan]

Originally posted by woodsracer144
so what size is a stock carb? whats the best 36 or 35? make like just a pwk?

I could be wrong, but I think a stock carb. is a 34PJ. If I'm wrong someone feel free to correct me.

[mxduner]

Originally posted by 1promodfan
I could be wrong, but I think a stock carb. is a 34PJ. If I'm wrong someone feel free to correct me. i believe you are correct

whats the best 36 or 35? make like just a pwk? they make a 35 pwk a/s or you can go with a mikuni tmx 35,36 tmx, which is not a favorite to some cause of jets availabilty. I own more mik jets than kehins seems sleds have mainly run them for years.

[woodsracer144]

what are some of your carb settings and motor set ups and stuff

[1promodfan]

Originally posted by woodsracer144
what are some of your carb settings and motor set ups and stuff

I live pretty much at sea level, I have a '89 w/ a new ESR 310 cylinder, TRX-9 porting, pump gas dome, hot rods crank w/ spacer plate, boyesen rad valve, stock air box w/ no lid, K&N filter, ESR TRX-9 pipe and an ESR silencer, 172 lbs. compression, and a PWK 36mm carb #5 slide, 172 main jet, 42 pilot, DGK needle on the 2nd clip from the top.

[Buttermilk]

This dyno chart is a direct comparison of a 41.5 PWK taper-bored carb to a 38 PWK A/S carb on my own 250R.

Motor is an OEM jug (67 x 76 bore and stroke) with my own porting, ESR11 in-frame center mount pipe, etc, etc, running Track Tek TT111 fuel.

In my opinion, the 38 PWK A/S carb is probably the best all around carb for the 250R, particularly the smaller sized engines.

Regards,

Rog

[woodsracer144]

ok, i was just gonna ask for dyno charts for a 35 36 38 and what ever else.

i have a LRD cylinder but i dont know if LRD just ported it or if its for a 300 sleeve in it... is there anyway to tell with out takin the whole motor apart... is there away to tell on the intake if its been resleeved?

i would also like to get some help gettin my carb set up right....

my elevation is sittin at about 1000-1500 ft, im running a LSR no link air box... it would be kinda like a normal air box with a K"N airfilter and a foam Prefilter...

i have a my carb set with a 170 main, a 62 piolt and the needle is on the 3rd clip... its in the middle.. my jets are the true Keihn they have K's on them... so what do you think i should do?

[mxduner]

Originally posted by woodsracer144
ok, i was just gonna ask for dyno charts for a 35 36 38 and what ever else.

i have a LRD cylinder but i dont know if LRD just ported it or if its for a 300 sleeve in it... is there anyway to tell with out takin the whole motor apart... is there away to tell on the intake if its been resleeved?

i would also like to get some help gettin my carb set up right....

my elevation is sittin at about 1000-1500 ft, im running a LSR no link air box... it would be kinda like a normal air box with a K"N airfilter and a foam Prefilter...

i have a my carb set with a 170 main, a 62 piolt and the needle is on the 3rd clip... its in the middle.. my jets are the true Keihn they have K's on them... so what do you think i should do? first thing to do is pull the head off and get some numbers off the top of the piston as well as measure it the best you can. I wouldn't suggest getting any jetting database from anyone seems the setups can be so different. find out your bore and verify you have the stock stroke etc.

next thing to do is find out which type of porting 'lrd' has done to this cylinder.That will be a lil tricky. Find out from whom ya got the motor from as it sounds like you didn't order the motor work originally?

that would be a decent starting point for now. Do a search there is sooo many jetting threads on here as well as esr's website in the faq? section, and check to make sure your carb's model (pj doubt it pwk or pwk a/s)


In my opinion, the 38 PWK A/S carb is probably the best all around carb for the 250R, particularly the smaller sized engines.

def. do not disagree with that, by far the favored setup. I would be interested in a key and mik shootout in the 38 category. the a/s vs. the tmx. o boy i bet i opened up me a can a worms this time. lol. As far as claims from reads they both have their place imo

[woodsracer144]

Thanks alot! How do you tell stroke?

[mxduner]

find bdc.(bottom dead center) and measure the distance the piston travels til top dead center. thats your stroke

[woodsracer144]

so what should i nmod on my carb to get rid of the lag it has... its on the ver low end... when i come out of a corner and i know i have to be slipping the clutch some times but I've never had something like this happen to me before.. thanks!

[Aceman]

Originally posted by woodsracer144
i have a my carb set with a 62 piolt

62 huh? I thought I had mine dialed in pretty close at 10 sizes smaller than that using a 52.

[woodsracer144]

im at about 100 to 1500 feet from sea level... if that means anything? what do these jets control... like the main pilot... like what part of the hit... like high low? or dont it really matter like if your sputtering in alot at low rpm it means your rich normally right?

[1promodfan]

Originally posted by woodsracer144
im at about 100 to 1500 feet from sea level... if that means anything? what do these jets control... like the main pilot... like what part of the hit... like high low? or dont it really matter like if your sputtering in alot at low rpm it means your rich normally right?

Its hard to tell someone how to jet because every bike/location is different. I had some of the same questions a while back and a lot of guys up here really helped me out a lot.

To me a 62 pilot sounds really fat. I can't say for sure but that could be part of you sputtering problem. When I changed mine it really helped a lot. If your sputtering you very well could be rich.

Trust me I learned the hard way.....start with your pilot first....make a couple of passes with just a little throttle (maybe 1/4-1/3), then get the needle right, then do your main last. Check out this sheet from Duncan, it has a lot of jetting info.

http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml

[woodsracer144]

Originally posted by 1promodfan
Its hard to tell someone how to jet because every bike/location is different. I had some of the same questions a while back and a lot of guys up here really helped me out a lot.

To me a 62 pilot sounds really fat. I can't say for sure but that could be part of you sputtering problem. When I changed mine it really helped a lot. If your sputtering you very well could be rich.

Trust me I learned the hard way.....start with your pilot first....make a couple of passes with just a little throttle (maybe 1/4-1/3), then get the needle right, then do your main last. Check out this sheet from Duncan, it has a lot of jetting info.

http://www.duncanracing.com/techfaq/Tech_keihin-carburetion-jetting.phtml

dude thank you so much... i totally for got about the great stuff on that site!

im gonna be reading up on that tomorrow when i wake up...

[woodsracer144]

hey guys, i did some work on my quad tonight and its all tore down... im getting my rear shock rebuilt soon and i had to take that off and im also getting ready for a new swinger so i have to pull that off as well but i noticed some leaking goin on on my clutch cover so i thought i would take a closer look in to that...
so i first pulled the exhaust off and took a better look and saw that i was leaking from the exhaust gasket and it looked like it was running down the side of the cylinder and ending up by the one clutch cover bolt... so i pulled the exhaust flange and i noticed that it looked kinda weird... it was like a golden brown but it didnt look right so i swiped my finger across it and it was all gummy kinda.. not really oily just really sorta gummy... so is it possable that the exhaust leak is making it look like a clutch cover leak as well? i also found out i need the little cap that you fill the crany with oil with because its striped out... so that might be the problem as well...

I also was feeling gutsy... i didnt really know what i had for a motor, for those who dont know i got Bob Linds only factory support quad and duncan set his motor up, i called them up and the motor use to have a PC2000 on it an i was really sad to find out that... because i dont have it... the cylinder thats on there right now has work from LRD done i thought it was just a Port and Polish but i took a look in the their site and i saw they had a 300 kit with a OEM cyl and it used o-rings, i was really looking in to it because i have a spacer plate and i couldnt see a little tap on the head gasket... but i was looking at the underside of the reed valve port and i couldnt see any righting, so i didnt reall know what to expect... so i pulled the cylinder head off and sure enough i had their 300 kit, i didnt right the piston numbers down but would this help explain the 62 pilot? or should i still be at about a 52?

since im takin it all apart... the exhaust was all blacked out and look just ulgy.... so i took a wire brush after it and got all the gayness off it... hers what she looked like