I think my carbs are to big

[fox_forma]

Basically I just got my shee together and right now it is stock stroke with a K&T dune port and its pretty aggressive. I am also running a set of shearer's sb inframes, milled and re-chambered head with +4 timing. Currently I have a set or PJ 34mm's on there with PODS and had it out at the dunes this past weekend. Basically I have all top end and nothing else. I can't really dune the bike and it will run through a 1/2-3/4 tank in about 8 miles of running it pretty hard which seems very excessive. I'm thinking the carbs are pretty much overkill yet this b!tch hauls ass when WOT and Rev's out great all through the high RPM's but I am looking for something that will keep my top end pulling strong but give me the down low snap as well if I just want to take a quick ride. We went on a semi decent ride and by the end of it I was dead tired due to having this sucker wide open through everything just so I didn't die out. Any ideas on what size carbs to shoot for at this point? I am also thinking about going to a twist throttle just for the dunes, my thumb never hurt so much before.

[Snopczynski]

Your pipes and port work are going to be the biggest factor on how your power delivery is. You more than likely have a very high exhaust port, and shearers are a top end pipe.

[locogato11283]

yep, id say your carbs arent the issue at all..

[jbooker82]

I would say your carbs match the port work and pipes. Change it all or leave it all alone.

[NOS_350x]

Ptr's would drop that drag motor down alot. A dune port shouldnt be ALL on top. So you get some low to mid pipes and hopefuly you hit a happy medium.

[Snopczynski]

It doesn't quite work like that. You have a high exhaust port, the pipe has to match it to work properly. He is going to have to change cylinders and pipes to get the power down lower at an earlier rpm.

[NOS_350x]

So are you trying to tell me that bike with the same porting that has OOF drag pipes and you swap to a 2 into 1 pipe Its not going to lower the rpm where your powerband hit is?

 

Its easy to change pipes to a lower hitting pipe, But you cannot change your porting once you go to a top end port.

[Snopczynski]

It will lower it to an extent, and make it an extremely innefficient running motor. The port heights in a motor are like the camshaft of a 2 stroke. You cant just mismatch parts and expect it to do what you want because you put a low end or midrange type part on it. The motor is ported to maintain a certain velocity and running efficiency. Its only going to respond to a point, and even then its going to be limited on its output. Thats why people say you cant have a bike that does it all. Shearers are reknowned for being a great topend pipe. K&T is well known for making great drag race motors. Hence, someone built a drag motor and put a drag race pipe on it. My guess is he bought it, rode it, and doesn't like the power delivery because he is play riding a drag motor.

[dajogejr]

My guess is he bought it, rode it, and doesn't like the power delivery because he is play riding a drag motor.

 

That's my take too....

Carbs are not the problem. Have you called K&T to see what they say....great group of people there!

[fox_forma]

I can handle the way the bike rides and really like the way the motor pulls, was just curious if carbs were and issue for not having any low end at all. I just assumed I would have more than whats there. It would just be nice to be able to play ride it a little than stay at comp hill all day. Maybe I will change it up, maybe not. Thanks for the info

[T_Shee]

yeah i agree that the carbs arent really your problem. mine has 35's on it with t5's and pods and no port work and it has pretty good bottom end and a ton of top. im going to go to 33's tho. for your thumbs sake i woiuld just cut down the springs on top of the slides. i thought my thumb would fall off one day so i cut the springs down drastically now its as easy as stock. it had a twist throttle when i got it and it was still hard to turn but not too bad i just hate twist throttles

[Frogger]

K&T Dune Port!!! That's funny. Do they make anything slow? They don't want their bikes being beat!

[FASTOYS]

Have you tried gearing lower? I would give Kim a call and ask him if he remembers the motor as it may something different than you were told. He will get you squared away.

[fox_forma]

I toyed with the gearing some but maybe need to go more drastic for the low end. I don;t mind how it really rides now, I mostly just dragged the bike but couldn;t really go on a normal ride due to working the hell out of it. Had to give lots of room to the person in front or else I would be right at their rear wheels soon and I was WOT. I'll give the gearing some more adjustments and see what it does, I just really like the top end on this thing and don't want to lose to much of it. I would rather fight it then lose the power. Thanks for the advise so far, i'll take step by step at a time.

[methyman]

I have a 4mm stock cylinder with a dune port job and it is the same way as you describe your bike is. It has 34pj carbs. It is a hand full in the tight trails. I put stock gearing on it and it was a different bike. I gain tons of low end. The bike is easier to ride. Just my $.02