so it's a '69, has the oem carb which i believe is a mikuni VM18sc ?

the "choke" is actually a starter jet, right?

are they're any carbs we can upgrade to before i buy a rebuild kit and go through mine? I pulled the baffle out of my exhuast, and at the moment i dont have a cover over the carb/oil pump as i removed the oil pump and still adjusting the carb. I would like to (in a perfect world) leave it off and slap a filter onto the end of the carb but it's an odd shape and would be hard to put a filter on.

treatland has a new age mikuni VM18 that i think will fit, but the choke level would have to be modified (whcih i wouldnt mind doing) to fit in the tight space it bolts onto the intake manifold in.

welp, came with a 180 in it. i put a 200 in it yesterday and it ran pretty good, a little better than with the 180 in it, still needed the starter jet here and there to help it. i think im going to get a complete carb rebuild kit for it and order a 210 jet for it aswell. i cant seem to find anything bigger than 210 though?

hope some of these updates help someone...

well i got a NOS carb rebuild kit off ebay, the bowl gasket was really all i needed but the new spring for the starter jet def helped and so did the new needle and float jet... etc, well worth the $20 i paid (iirc?)

well that mixed with a 240 jet i tracked down on amazon with the part number, she runs GREAT now! keep in mind the baffle is out of the exhuast and the carb is pretty opened up sucking in air unrestricted
first gear is a little bit of a dog but 2nd and 3rd work great. i think im going to upgrade the idle jet from #20 i wanna say it is to a 30 or 40 and see what that does. i understand i may have to back the main jet back down to a 230 if i do this but we'll cross taht bridge when we come to it. regardless after she warms up she's running awesome!

probably do a top end this summer NOS piston and rings are pretty cheap

i stand corrected... after a while she started bogging

put the 180 main back in it and left the 115 pilot...

Started flooding on me now :(

i think the pilot is too big? ordered an 80, 90 and 100 to try

geez the money i have in jets! if anyone needs some please pm me, i now have 240, 230 220 200 175 170 160 140 120 100 90 80 70 MAIN JETS

&&&&

130, 115, 100, 90, 80 pilot's


Picked up a late 70's DT100 which has a 5spd on it... if i cant get this 47 year old engine to run i may swap the dt100 (97cc) onto it

Those jet sizes sound awfully big... especially the pilot jets.

I would do a crankcase pressure/vacuum leakdown test. You might have a crank seal leaking.

+1 on the pilots' size. They are usually 15-30 stock, depending on the size of the engine...

shoobs, I think I'm the owner of your 69 Trailmaster ! I finally pulled it out from under a tarp today and fit everything up. Had to order the right plugs but got spark once I hot wired the ignition switch. I know it's been a while, but at the end was it running on a smaller pilot or did you give up ? Also, I think I have all the pump stuff but would rather leave it off, is it blocked? If not, how/where do I do that ?

Man, I just looked through 4 of those new huge pilots you tried. Those holes are HUGE ! Usually I can barely see through ones in the 20 to 45 range. 130 pilot....phew....definitely was the flooding problem....hehehe....

Rich

Kind of a reference, my Trailmaster 80, has 120 main and 25 pilot

I'm going to open up the carb, but if the pilot in there is the third big one he listed I'll have to pick up the stock 20 and maybe a 22.5 and 25. The stock main was definitely a 180 so will probably go up to a 200 since the exhaust baffle is missing and the only intake I have is the boot off the case and a small K&N. I'm stoked I got spark and an easy button....she should be on the road soon.

Can anyone tell me where to check for the oil pump block off plate? Is that so oil mist doesn't come out where oil used to drip in ? I guess it's a compression in the crankcase thing too or is that on the other side of the crank seal from the cylinder?

I'm really getting excited about this little bike, SO easy to work on. It was slightly cafe'd when I got it but very tastefully done, will be a great companion at the Home Depot car gathering to my 72 Yami R5C !

In my limited experience unless mods or altitude Yamahas are pretty well jetted from the factory. If you got leaky seals and it doesn’t want to idle or it overruns then fix that then see where the jettings at. Sorry if I missed
That you have mods if you do.

Can almost guarantee 50 year old o rings on the right crankcase. The rotary valve. And on the crank pin collar are going to be a bit shrunk. The seals will be rock hard as they always are. When I’ve rebuilt the motors on my 2 Yamaha they have run perfectly with stock carbs and netting until I did some porting and mods.