So my original carb on my ‘03 Blaster has been rebuilt at least 4 times. I decided to replace it with a new one and keep the original as a spare. So I go to my handy dandy local Yamaha shop and they set me up with a new VM 26 carb from western power sports(see pic) with no TORS cap so I can remove that POS while I have everything apart. Problem is, this new carb seems to be bigger. It has a longer body from the mouth of the air box inlet to the mouth of the manifold. It also has a different style of float and a different needle. Even the slide is a larger diameter. The inner diameter of the flow thru chamber is the correct size, however. Not being a carb guru I decided to get you folks opinion on whether I should try this carb or take it back and go another way. Is this just an updated design on an old part that has improvements but doesn’t effect the overall operation or the part? Any advice is appreciated. ‘03 Blaster with Toomey exhaust and open air box. Running a 290 jet.
It’s the 28mm VM carb on page 378 of this catalog link. Any advice is greatly appreciated
New Carb
- Thread starter gaiden
- Start date
Ok, original carb cleaned and rebuilt(again), installed. Starts on first kick(great!). Isles like a champ! Bogs as soon as I hit the throttle. So use a smaller jet, maybe? It’s got a 290 in right now. I’m not sure how low I should go with the Toomey exhaust and open air box. Any suggestions?
I'd like to know what and why you're "rebuilding" on this carb so many times ?
rebuild kits ? genuine mikuni jets ?
290 sounds lean for a Toomey exhaust
what did full throttle plug chops tell you ?
pilot and air screw setting effect idle to 1/4 throttle
1/4 to 3/4 throttle is the job of the needle and it's clip setting
the main jet kicks in after 3/4 to full throttle
float height effects all jetting ranges
what throttle position are you experiencing this new bog ?
that's the jetting circuit you need to adjust
look in the carb section here for DIY's on float heights, pilot/airscrew, and plug chops
rebuild kits ? genuine mikuni jets ?
290 sounds lean for a Toomey exhaust
what did full throttle plug chops tell you ?
pilot and air screw setting effect idle to 1/4 throttle
1/4 to 3/4 throttle is the job of the needle and it's clip setting
the main jet kicks in after 3/4 to full throttle
float height effects all jetting ranges
what throttle position are you experiencing this new bog ?
that's the jetting circuit you need to adjust
look in the carb section here for DIY's on float heights, pilot/airscrew, and plug chops
I bought this quad about 5 yrs ago. The owner then had said the carb was freshly cleaned and rebuilt after sitting for over a year. This was the 2nd rebuild.
My job and having 3 kids between 7-16 unfortunately leaves me with large spaces of time when I’m unable to do much of anything outside of work much less set aside time to ride. I’ve had my local Yamaha dealer clean and rebuild it once since I bought it. That was around 3 yrs ago. I rode regularly with no issues for about a year when I was sent on a new assignment at work. Since then the quad has sat until recently. As it sat so long the carb again needed to be thoroughly cleaned and rebuilt. The reason I opted for a new carb this time is I was hoping to keep one clean and ready for when I have time to ride so I could just swap them out and go from there cutting my set up time considerably. I’ll get a new set of Mikuni jets and new needle and start this again. To answer your other question, it starts 1st kick and idles fine, but as soon as I touch the throttle it starts to bog. I’ll go back thru the carb again with all genuine Mikuni parts and see what happens. As far as plug chopping I haven’t done that yet as it won’t run above an idle. My Yamaha shop did do it when they did the service. I don’t have the old plugs from 3 yrs ago, but it was tuned accurately.
If I’m going about this wrong, please tell me.
My job and having 3 kids between 7-16 unfortunately leaves me with large spaces of time when I’m unable to do much of anything outside of work much less set aside time to ride. I’ve had my local Yamaha dealer clean and rebuild it once since I bought it. That was around 3 yrs ago. I rode regularly with no issues for about a year when I was sent on a new assignment at work. Since then the quad has sat until recently. As it sat so long the carb again needed to be thoroughly cleaned and rebuilt. The reason I opted for a new carb this time is I was hoping to keep one clean and ready for when I have time to ride so I could just swap them out and go from there cutting my set up time considerably. I’ll get a new set of Mikuni jets and new needle and start this again. To answer your other question, it starts 1st kick and idles fine, but as soon as I touch the throttle it starts to bog. I’ll go back thru the carb again with all genuine Mikuni parts and see what happens. As far as plug chopping I haven’t done that yet as it won’t run above an idle. My Yamaha shop did do it when they did the service. I don’t have the old plugs from 3 yrs ago, but it was tuned accurately.
If I’m going about this wrong, please tell me.
Another thing to remember is what you're describing as "bogging" can occur when you are way too lean as well. If it's dying out right at the beginning of your throttle curve, I wouldn't mess with the main jet until you can get to it. At the front, you're running on the pilot and jet needle settings. Double check your needle taper and clip position. Make sure your air mixture screw is set before all else. Good luck!
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