Hi!
I visited my parents' farm last weekend, and took the occasion to mess with my '72 TS185 that I've been keeping there.
I just figured out was was making it run so poorly, and I thought I'd share the tip.
First, I had cleaned out the carb thoroughly. It had been suffering from a plugged pilot jet, of course, so it wouldn't idle. It wouldn't run well at high rpms, either, but that may or may not have been related.
Anyway, with the carb cleaned out, the bike idled well, and ran good right up to about 3/4 to full throttle, where it "blubbered" - making that characteristic four-stroke sound and having NO power.
I assumed that it was running rich at those RPM's, and verified this by flipping off the fuel petcock while riding - just before the bike ran out of gas, the top end power returned.
First, I checked the air filter and the exhaust pipe and exhaust port. Running without the air filter didn't help things. Neither did running the exhaust unbaffled, and the exhaust port was clean.
So... I thought maybe I would experiment with leaner main jets, but I took the carb apart again - and then I found the problem.
The jet that the needle rides in is a long brass tube. This tube has an O-ring at the bottom that seals it into a small chamber for the main jet when the bottom of the float bowl is attached. This O-ring had become deformed and hard from 30 years of sitting there, and it was allowing gas to leak in around the main jet, resulting in an over-rich situation at 3/4 throttle and above.
I visited my local Suzuki dealer (Yeager Cycles, Sedalia, MO) and was disappointed to find that they have turned into a Harley clothing boutique...! I asked the guy at the parts counter. No, I couldn't buy just the O-ring, and I also couldn't buy jets other than the 130 main that was stock for it. :coocoo:
Anyway, I got a set of ten O-rings at Lowe's for a buck-and-a-half (I think they were #63, but I'm not sure). They were an exact replacement, and now my top-end has returned to my TS!
So, if you are messing around with an older bike with a Mikuni VM carb, make sure to replace that crusty O-ring in there - it will kill your top-end jetting.
It made me wonder if the old Yamaha DT-1 I used to have was suffering from the same malady... could have been.
I visited my parents' farm last weekend, and took the occasion to mess with my '72 TS185 that I've been keeping there.
I just figured out was was making it run so poorly, and I thought I'd share the tip.
First, I had cleaned out the carb thoroughly. It had been suffering from a plugged pilot jet, of course, so it wouldn't idle. It wouldn't run well at high rpms, either, but that may or may not have been related.
Anyway, with the carb cleaned out, the bike idled well, and ran good right up to about 3/4 to full throttle, where it "blubbered" - making that characteristic four-stroke sound and having NO power.
I assumed that it was running rich at those RPM's, and verified this by flipping off the fuel petcock while riding - just before the bike ran out of gas, the top end power returned.
First, I checked the air filter and the exhaust pipe and exhaust port. Running without the air filter didn't help things. Neither did running the exhaust unbaffled, and the exhaust port was clean.
So... I thought maybe I would experiment with leaner main jets, but I took the carb apart again - and then I found the problem.
The jet that the needle rides in is a long brass tube. This tube has an O-ring at the bottom that seals it into a small chamber for the main jet when the bottom of the float bowl is attached. This O-ring had become deformed and hard from 30 years of sitting there, and it was allowing gas to leak in around the main jet, resulting in an over-rich situation at 3/4 throttle and above.
I visited my local Suzuki dealer (Yeager Cycles, Sedalia, MO) and was disappointed to find that they have turned into a Harley clothing boutique...! I asked the guy at the parts counter. No, I couldn't buy just the O-ring, and I also couldn't buy jets other than the 130 main that was stock for it. :coocoo:
Anyway, I got a set of ten O-rings at Lowe's for a buck-and-a-half (I think they were #63, but I'm not sure). They were an exact replacement, and now my top-end has returned to my TS!
So, if you are messing around with an older bike with a Mikuni VM carb, make sure to replace that crusty O-ring in there - it will kill your top-end jetting.
It made me wonder if the old Yamaha DT-1 I used to have was suffering from the same malady... could have been.
