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Carb advice?

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Ok guys I bought a 400 and it came with a keihen 2 stroke carb on it, not sure why someone would do that. (any thoughts on that?) it runs really good, but the throttle response isn't crisp and it has an annoyingly long throw. I am thinking about either buying a used xr carb or buying a powernow and a throttle tube with a shorter throw. (do they even make those?) does anyone have any advice? I have a race bike that I throw most of my money at, this is just a fun dual sport bike so I don't really want to drop the $ on a pumper carb. Suggestions?

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That's because the stock carb is known for being not so great, especially in California. Stock carbs can be set up ok with proper jetting but you will never get a real crisp snap from them because they are not a pumper carb. Have you changed any of the jetting? The previoius owner might have just slapped it on there and decided it ran well enough. You can get an adjustable throttle, it will come with 3 cams, faster, stock and slower.

http://www.motosport.com/dirtbike/product/G2-ORIGINAL-THROTTLE-CAM-SYSTEM-CLEARANCE/?catalogId=109153

What is the model of carb you have and do you know what bike it is from? Is the stock XR throttle tube still on the bike or did they replace it? I think the stock XR has a different ratio than most 2 stroke bikes so if they didn't replace the tube that might be part of your problem and you could just buy a cheaper 2 stroke setup rather than the expensive adjustable one.

Is there anyway you can post some pics? The usually replacement pumper carb is a Mikuni or Edelbrock so it would be interesting to see how someone got the Keihin to work.

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I'll post some pics tonight. I'm taking it on a ride tomorrow and I don't want to tear it appart so it may be with the tank on.

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What ATJ said, there are lots of guys that are running aftermarket carbs. Should be lots of stockers out there for cheap.

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What ATJ said, there are lots of guys that are running aftermarket carbs. Should be lots of stockers out there for cheap.

Not just cheap, but well tuned!👍

We've had good results with proper tuning on the stock 38mm Keihin carb, thanks to the shared experience of others on this site.🤣

Perc

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Hey not sure what cheap would be, but I would quite possibly be interested. Let me know how much you would be willing to sell it for. You can pm me if you want. Thanks:)

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Hey not sure what cheap would be, but I would quite possibly be interested. Let me know how much you would be willing to sell it for. You can pm me if you want. Thanks:)

PM sent 👍

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I'm running a Mikuni VM 32 on a XR 250. It has a two stroke type Nozzle jet, which is the only major jetting difference between 2 and 4 stroke carbs. I must of hit the jetting really close. My bike runs and starts better than it ever did with the stocker or with an Edelbrock.

You need to measure the inside diameter of your carb. It maybe to big for the 400. Or it is poorly jetted. You can do a search here and find what is the best size for a 400.

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