175 carburetor

[ddog71]

The carburetors on the 175 are marked as "VM17-18". Does anyone know the differences between the Mikuni VM17 and VM18 carburetors.? There's an ebay seller ("niche-cycle" in Florida) that sells the VM18. I just purchased a float from them that sure looks like it fits the 175's carb. Thanks... Tim 

[Redrust]

from some QUICK measurements on a spare carb i have it seams to me that the 17mm is the intake air port diameter at the nearest part of the throttle slide. it looks as though the VM17 and VM18 are very close in matching so a float should work its just the difference in the intake port opening that seams to be the difference. could be that its 17mm on one side of the slide and 18mm on the other.

check on the return policy of the ebay seller and ask questions if in doubt. check for matching specs when you get the part and see if you can set it correctly on a dry carb so if you need to send it back he won't have any reason to complain about restocking with a smell of gas on it.

good luck.

[ddog71]

Thanks. Got my digital micrometer out and measured the float I had removed from the "gunked up" carb. The measurements I got are approximately: 51.5mm overall width; 20.5mm distance between floats; 30.5mm float diameter.

[disc_valve]

Yes, the VM17 and VM18 carbs are identical apart from the main bore being bored out to 18mm on the VM18 version. By stamping VM17-18 in the casting mould Mikuni were able to use the same basic casting for two sizes of carb to save on production costs. On Brisgestones, the 17mm version was only used on the 90 Sport and 175 Dual Twin. The 18mm version was fitted to the 175 Hurricane, and all the various 100cc and 200cc models.

I don't think it makes a great deal of difference which carb body you use, so long as the Throttle slide and jets are set up for your engine by the book. When I came to restore my 175 Dual Twin a few years back, I discovered that I'd been riding around on it for nigh on 20 years with one 17mm carb and one 18mm carb fitted. I couldn't detect any running problems with that set-up, but it's probably better to fit two carbs of the same size on a twin if you have a choice. Otherwise, don't get too concerned.

Graham   

[ddog71]

Graham, thanks for that info. What I've been doing since joining this site is to print out questions and answers from this forum and putting the printouts in a three ring binder for future reference. I have a really crappy memory and it has only gotten worse as I've gotten older.!! Thanks to you and everyone else for all the helpful information..... Tim