puch magnum mkII bogging down & not much power

i recently got a non-running '79 puch magnum mkII. it seems to bog down when i give it gas, and when i finally do get 'er revving as high as she'll go, there's almost no power...if i try to go up an easy incline she'll slow down and eventually just not go any further.

i've de-rusted the gas tank, cleaned the fuel line and carb, made sure the airbox is breathing, it's got a newish biturbo exhaust, and cleaned out the cylinder.

anyone got any ideas? thanks alot.

Re: puch magnum mkII bogging down & not much p

clean your airbox, run a plug chop, put in a new plug and check your timing.

Re: puch magnum mkII bogging down & not much p

Did you put a larger jet in when you installed the Biturbo?

You need a #68 or #70 jet depending on the size or the carb!

Re: puch magnum mkII bogging down & not much p

alright...got a new plug(tho the old one was in good shape), got a larger #70 jet, the airbox was perfectly clean, and still no power....it runs, but has no pep at all. any other ideas? thanks for the tips, folks.

Re: puch magnum mkII bogging down & not much p

maybe your timing is messed up. i had a motobecane that had NO POWER and i mean NO POWER and all i had to do was adjust the timing. there are many dispshits out there and who knows who has been messing with the bike before you got it.

Re: puch magnum mkII bogging down & not much p

You could have a compression leak somewhere. You can get a compression tester at Sears for $25. You are supposed to hold the throttle wide open while testing. If you don't want to shell out for a tester, you could try spraying some carb cleaner around your head, base, and crank gaskets... if you hear an increase in RPMs, you'll know it's sucking in air there.

Re: puch magnum mkII bogging down & not much p

Have you changed the tranny fluid?

If it is over-filled it will cause symptoms like what you are describing :P

Re: puch magnum mkII bogging down & not much p

As you can see, it's hard to isolate LOP problems without a lot of troubleshooting. All of the scenarios offered here could cause power loss. If it's been sitting a while, the first thing I would check would be compression (which could be leaking as far back as the transfer seal in the crankcase - most non-running Garellis I pick up have that problem), although I did see a Magnum with the clutch cable too tight run like that - your clutch could be staying engaged.

Re: puch magnum mkII bogging down & not much p

is your bike loud, like louder than you would expect? is so, your pipe is probably loose. Those biturbos aren't meant to fit on magnum cylinders or frame. and a too large jet. (my guess. but my ported cylender can't even go above 72, and i've been working on a magnum for like the last three hours.) Oh and it works great for power to advance your timing all the way. (turn stator plate all the way clockwise for two-speed, counter for 1-speed)

hope this helps/

Re: puch magnum mkII bogging down & not much p

They do make a modified Biturbo with an angled pipe that fits the Magnum :P

Re: puch magnum mkII bogging down & not much p

frat, can you just use the header from a regular magnum pipe with the Bi-turbo, or would you be wasting your time? Basically, is the Bi-turbo header bigger than the magnum one? Or, is there a way to start out w/ the regular header and then weld the Bi-turbo on at some point?

Re: puch magnum mkII bogging down & not much p

The Biturbo header isn't that big so they may be the same... you could probably measure it and compare the two..

I have a Stock pipe here somewhere and I'll dig it out later and take a look at it side-by-side and let you know!

The only difference in pipes is the header pipe so I don't see any problem as long as it is as open as a regular Biturbo :P

Re: puch magnum mkII bogging down & not much p

i didn't know they made magnum biturbos, or is this one of those home-brewed deals?

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account