I have a TR1 engined wasp sidecar motocross outfit.I know as standard it has 40 mm cv carbs  mine came with 36 round slide Mikunis but didnt run very well. At the weekend I tried some 40mm Dellorto and it did perform better .It uses K and N airfilters and 2  car silencers.What would you think is the best size slide carb to use?Paul

papsck wrote:

I have a TR1 engined wasp sidecar motocross outfit.I know as standard it has 40 mm cv carbs  mine came with 36 round slide Mikunis but didnt run very well. At the weekend I tried some 40mm Dellorto and it did perform better .It uses K and N airfilters and 2  car silencers.What would you think is the best size slide carb to use?Paul

Stock size is a 40mm Hitachi CV carby. Rule of thumb says, that a CV carb will only allow about 2/3 of the available diameter to be used, both the 36mm (I suppose they were Mikuni VM36) and the 40mm Dellortos should be fine. In terms of jetting... hmm... I would stick with the Mikuni VM because the slides are hardcoated, whereas the Dellorto carbs are brass only (with a thin plating of chrome) and therefore wear out a lot faster, especially in terms of the needle jet - trust me, I know... I have been riding old KTMs for quite a while).

Mikuni VM36 jetting (no responsibility taken, but this is roughly how my XT500 is jetted, which could be called "half a TR1 engine")

Pilot: 25
MainJet: 120 or 125 (go for the richer jet to start with)
JetNeedle: Middle position (3rd notch in my case)

This should (with some fiddling) at least give you some sort of idle and then try to adjust the mixture-screw (which is on the front towards the engine) about 3 full turns (+/- 1 turn). This should give you something that should be rideable. Once you're this far you should check the plugs and see what color they are and whether you have any flat spots or the like.

Hope this helpful in any way to you

Cheers,
Greg

Hi, my name is Didier. I have an xv 1000 tr1 '81 model and i recently visited a local yamaha dealership to find out what spares are available. seem there are still some spares for the motor. however the spares i required was for the carbs, and they are longer in manufacture. I noticed you were talking about different carbs. and mentioned 36 and 40 mm carbs. my question is this what would the ideal carbuartor be for this motor? single or double carb? side draft even maybe? reason i am able to machine manifolds if it deem necessary. I really enjoy these model bikes. Any recommendations?