hi all my bultaco as been sat for a wile since restoring it the petrol as been in the tank for roughly 6 0r 7 months she starts up ok normaly takes a few gose when shes not been run for a wile i had her runing today started up 3thd kick ticking over no probs had a ride round the garden shes dosent seem to be pulling as she did know ive not done anything to her would it be possibel that the petrol as gone stale? hence loss of power

clean carb, jets probably partly blocked.

clean carb, jets probably partly blocked.

its a brand new makuni carb so should it still need cleaning? like i said the fuel as been in for quit a wile i mean it dose run ok just dosant seem to pull like it did ill have to get some carb cleaner

its a brand new makuni carb so should it still need cleaning?

Yes. Firstly the Mikuni MAY have been supplied wit anti-corrosion stuff on the inside (a bit like new disc brakes are). Secondly some of the goo in the tank (sometimes the 2T oil comes out of solution and settles at the bottom of the tank) may have made it through to the floatbowl and has blocked the jets. Thirdly when petrol sits it loses octane rating. It's possible that the octane rating has dropped so much that it's useless. This will need to be cleaned/emptied from the float bowl.

As well as those things Tim said, if the fuel evaporates out of the float bowl over time (fuel tap off and does not pass), it leaves a viscous oily residue coating on everything that it was touching that takes a while to wash off when you turn the fuel on next time. I find that I get restriction in the pilot jet from this residue that makes the bike run poorly for a few minutes after not being run for a few weeks. With longer term storage (with the fuel tap left on or passing) a solid polymer film can form on the surfaces that the petrol touches and it can be very difficult to remove the film.

As well as those things Tim said, if the fuel evaporates out of the float bowl over time (fuel tap off and does not pass), it leaves a viscous oily residue coating on everything that it was touching that takes a while to wash off when you turn the fuel on next time. I find that I get restriction in the pilot jet from this residue that makes the bike run poorly for a few minutes after not being run for a few weeks. With longer term storage (with the fuel tap left on or passing) a solid polymer film can form on the surfaces that the petrol touches and it can be very difficult to remove the film.

Got the same problem. What's the best way of cleaning a carb that's been gummed up like this. Bog standard carb cleaner? Or is there something better?

Got the same problem. What's the best way of cleaning a carb that's been gummed up like this. Bog standard carb cleaner? Or is there something better?

I the gum isn't too old, (some kind of slimy), a carb cleaner will do the job, even normal gas and diesel oil. When it got gelantinous a carb cleaner may get it dissolved may be not. Then you can give the carb to your next shop where they have a ultra soni cleaner. If the gum got "crusty", (couple of years and some other weirdo debris show up too then this can bee a real issue), looking like this:

As "our" new gas don't have a long storage time, I drain the carb, (and gas tank), for longer storage period then two weeks.