Post by paulbeard on Jun 25, 2019 15:06:36 GMT
Nice to post something other than "what's this?" or "Does anyone want one of these?"...I finally had some time to spend on the 250N so I took the carbs off the bike yesterday - it was fairly straightforward, one of the screws for the Insulator into the cylinder head was reluctant (yup, the one that's tricky to get to). Turns out the offside Insulator had a jubilee clip rather than the proper item fitted and the offside airbox rubber didn't have a clip on it at all. I'm guessing that won't have helped the mixture.
Stripping down went well - Buster's guide was invaluable. One stripped screw on the nearside carb top cover, but that was the only one of those which was a surprise. The springs for the vacuum piston might need changing as they were ok with the piston held horizontally but wouldn't push the piston up vertically like on Buster's video example. Also, the small rubber o ring was missing completely from under the air stop valve cover on the nearside carb. Other than that, that carb wasn't too bad, apart from the expected bloackages in the various jets.
The offside carb wasn't missing anything but it was much worse in general for gunk, especially in the air stop valve.
In both carbs the O Rings under the top covers were stepped side down, not up as per Buster. It looks like the previous owner has been in there as the rubber bungs were new looking and the float needles look like new items (which makes me doubt that the float height was adjusted correctly - the nearside carb had a permanent drip from the overflow). The more obvious jets had been previously changed/cleaned I think but the hidden ones, the tube you unscrew with a spanner and the needle nozzle didn't seem to have been touched, given the tarnishing and blockages.
I've got a couple of sets of carbs in my box of bits that came with the bike so a couple of screws will get borrowed and hopefully a couple of those piston springs might be a bit stronger.
The only other thing I noticed was that the carbs off the bikes were VB30B with a B in the square box, is this a slighter later carb than the one in Buster's guide?
So now they're ready to take down to a local bike shop for ultrasonic cleaning. Estimated cost is half that of buying a cleaning tank myself and I may get them to also refit the carbs onto the bike and get them balanced properly with vacuum gauges.
Anyway here's a before and after shot.
Thanks again to Buster for the excellent guide!
Stripping down went well - Buster's guide was invaluable. One stripped screw on the nearside carb top cover, but that was the only one of those which was a surprise. The springs for the vacuum piston might need changing as they were ok with the piston held horizontally but wouldn't push the piston up vertically like on Buster's video example. Also, the small rubber o ring was missing completely from under the air stop valve cover on the nearside carb. Other than that, that carb wasn't too bad, apart from the expected bloackages in the various jets.
The offside carb wasn't missing anything but it was much worse in general for gunk, especially in the air stop valve.
In both carbs the O Rings under the top covers were stepped side down, not up as per Buster. It looks like the previous owner has been in there as the rubber bungs were new looking and the float needles look like new items (which makes me doubt that the float height was adjusted correctly - the nearside carb had a permanent drip from the overflow). The more obvious jets had been previously changed/cleaned I think but the hidden ones, the tube you unscrew with a spanner and the needle nozzle didn't seem to have been touched, given the tarnishing and blockages.
I've got a couple of sets of carbs in my box of bits that came with the bike so a couple of screws will get borrowed and hopefully a couple of those piston springs might be a bit stronger.
The only other thing I noticed was that the carbs off the bikes were VB30B with a B in the square box, is this a slighter later carb than the one in Buster's guide?
So now they're ready to take down to a local bike shop for ultrasonic cleaning. Estimated cost is half that of buying a cleaning tank myself and I may get them to also refit the carbs onto the bike and get them balanced properly with vacuum gauges.
Anyway here's a before and after shot.
Thanks again to Buster for the excellent guide!