I need the boot that comes from the airbox to fit over the carb,I have a 38mm and my stocker is too small. I've tried looking up different year CR 250's but they all seem to be oval shaped and bolt in instead of the round kind with a band clamp like mine.I need to use my airbox or I would just clamp a filter on the carb.Is there a certain stock part from another machine or an aftermarket boot? Any help appretiated.

 

When I got my 38mm Mikuni carb I got my stock boot to fit on the carb. In the instructions with the carb it said to use alot of wd-40, but the stock one would fit. I used alot of wd-40 and alot of elbow grease to get it on. I also shaved a little of the rubber from the inside of the boot. Even with all this, everytime I had to work on the carb, I had to work at getting it back together.

 

Everybody has this same problem when going to a larger carb. I installed a 38mm airstryker and had the same problem. You can do a couple of things to make it work. Get a hair dryer or a heat gun and heat up the end of the boot to make it more pliable or you can dip the end of the boot in some very hot water for the same results. Once it's more pliable, it's 100% easier getting it to fit over the larger carbs, then get a hose clamp and clamp it down tight.

 

Yep, Heat that boot up and it will fit.

 

If you can find a glass Pepsi bottle it's the perfect size, I greased the bottle, heated up the boot and installed the bottle inside the carb end and left it for a couple days. It slips right on then, you can also buy an 86 boot that doesn't have the boost bottle on the side which will slip on easily being new and soft.

 

I have had the boot on there but its distorted and a couple inches upstream of the joint the boot actually gets smaller.I look at it this way I bought the 38mm to flow more air/fuel.If the opening in my carb is larger than the minimum diameter (tightest spot) in the boot that feeds it I am essentially running a restricer plate right? Or does it not matter because the boot is still bigger than the actual 38mm opening in the engine side of the carb? I don't know but I would like to find a cone shaped boot off anything I could get my hands on to see if it would work/run better.

 

Does anyone know if a bigger or different boot comes with an aftermarket airbox?

 

Trust me the bottle trick will really open up the boot, leave it on the bottle a couple days and hit it with a heat gun or hair dryer a few times.

 

Ok thanks, I think my biggest problem is the fact that mine is probably 15 years old and its more like plastic than rubber.I guess I'll order another one and try it, probably be alot more pliable.

 

Heating the boot will soften it, I did mine on an 87. Installed it on a 38A/S no problem. My 88 I just assembled with a new boot for an 86 that doesn't have the boost bottle (or whatever it is) it went on without heating as the boot was soft but you can get yours to work.