I have a Yamaha blaster project I'm working on for my son it has b1 pipe and silencer,bored .04 over with Vito's forged piston kit, 3mm stroker crank,vforce 4 reeds,aluminum open air box with outer wear and k&n filter,have a 28mm carb that's jetted but was wondering if a kiehin 34mm PW would help open it up a little more or would that carb be to large
what carb should I run
- Thread starter Curtis71
- Start date
Sorry but yes it has been completly built with port and polish Duncan's did all the motor work
Is it a 28PWK we are talking about? The one advantage I see between the 2 carbs you have in your situation is that the 28pwk will squeeze into the existing intake boots. The 34Pj will need new boots to work. Just some food for though.
The B1 is a mid/top pipe and a larger carb will allow it to work better in the area is is designed to perform.
Low/mid pipe, smaller carb, mid/high pipe, larger carb!
Low/mid pipe, smaller carb, mid/high pipe, larger carb!
When i had my stock carb and right bend pipe i felt it was sluggish. there was no good spot for power.
Now that i run a 35mm carb with the right bend i have tons of power i can use.
if a B1 is truly a top end pipe, you may want the larger carb on it
Now that i run a 35mm carb with the right bend i have tons of power i can use.
if a B1 is truly a top end pipe, you may want the larger carb on it
The own 28 is an excellent carb choice, you will still retain the low end punch but have to big top end togo with it, the 34mm is gonna effect your low end response, if any thing, I'd have the 28 bored to a 30, thats what my carb is, I run a Toomey aswell
When you go to a larger carb you lose the momentum of the air column.
The Blaster motor needs this momentum to ram enough mixture through the piston window in the small time available, which is less than half the time a typical case valve engine has available. This is why the Blaster motor works better with a smaller carb and the long skinny air cleaner boot. Larger carbs have slower flow speeds and do not have the momentum.
Stroker engines trade displacement for RPM and often do not gain any maximum HP for this reason. What they do gain is more mid-range torque, which does not require a larger carb.
Just words prove nothing, experience does. It takes minutes to swap a carb and boot if needed. My son and I experimented with various carbs from stock through to 39mm. Try back to back testing and report back to us.
Steve
Blaster carb vs 39mm Keihin, 28, 32, 34mm carbs also tried.
The Blaster motor needs this momentum to ram enough mixture through the piston window in the small time available, which is less than half the time a typical case valve engine has available. This is why the Blaster motor works better with a smaller carb and the long skinny air cleaner boot. Larger carbs have slower flow speeds and do not have the momentum.
Stroker engines trade displacement for RPM and often do not gain any maximum HP for this reason. What they do gain is more mid-range torque, which does not require a larger carb.
Just words prove nothing, experience does. It takes minutes to swap a carb and boot if needed. My son and I experimented with various carbs from stock through to 39mm. Try back to back testing and report back to us.
Steve
Blaster carb vs 39mm Keihin, 28, 32, 34mm carbs also tried.
I ran both a stock and pj34 on my blaster with ported cylinder, high compression head, and trinity pipe.
With the stocker it was pretty sluggish all throughout the power band. And it wasn't that fun because it didn't have much pull up top.
With the the 34 I felt it was more responsive everywhere. And when you got it up in the upper part of the rm range it really screamed.
Just speaking from experience. But I far prefer the larger carbs when porting and mid/top end pipes are involved
With the stocker it was pretty sluggish all throughout the power band. And it wasn't that fun because it didn't have much pull up top.
With the the 34 I felt it was more responsive everywhere. And when you got it up in the upper part of the rm range it really screamed.
Just speaking from experience. But I far prefer the larger carbs when porting and mid/top end pipes are involved
Well I'm going to be running a 4 mil, aggressive trail port with Lrd and vforce 4's....no since in upgrading carb if I don't upgrade the airbox too...
I have had stock carb, PJ34, 35 PWK, and a 38 PWK. The 38 is still on there
The main problem with the bigger carbs and why they get a bad rap is not many go thru changing the slides and needles to get them to work on these smaller cc engines (as you and I have done)
Most throw them on as they were tuned for the bigger bikes and wonder why they don't perform good.
Just changing pilots and mains can get them to idle and maybe run WOT. But without changing slides and needles, the mids where 75% + of riding is done.... will suck at best.
No jet kits will have what you need, required is a #6 slide, dgh or cel needle, 45-50-ish pilots and 148 - 155-ish mains.
Wow alot more in depth than I thought..... anyone ever get one to work with a 4 mil stroker? I guess start in the middle and work with it, where I ride the most it's about 5-15ft above sea level
