12 replies to this topic

[bambam_n_chunx]

Help, i`ve totally rebuilt a fantic 240. Engine work done includes new mains,seals and bigend. Whilst the barrel was off I checked the barrel and piston which still had its machining all the way down.The ring gap appeared fine. I`m running 11/39 sprockets and the carb is in excellent condition with as new slide and needle as is the silencer
Yet the problem is the bike struggles to pull 2nd gear through the sections and if I try to use 1st all the time it struggles to find grip. Can anyone offer any suggestions. I think the carb is set up right, I checked the jets and changed the main after reading a Lee Harris thread but it hasn`t made much difference.
Also can anyone recommend a better chain tensioner as the standard one doesn`t seem to be much use.
Cheers
Andy

[Stork955]

Gday, have you cleaned the front pipe?


Cheers,


Stork

[bambam_n_chunx]

No, I`ve never needed to this with bikes before so never gave it a thought, how is it done and whats in the expansion chamber.

[Heavydabber]

bambam_n_chunx, on Nov 23 2009, 08:51 PM, said:

No, I`ve never needed to this with bikes before so never gave it a thought, how is it done and whats in the expansion chamber.

Be careful with the front pipe as the expansion chamber is lined with a layer of sound-absorbent material (read fibreglass wool) behind a metal mesh skin that keeps it all in place, check the u-bend at the front of the pipe to make sure its not coked up also same thing with the outlet to the silencer.......but did it run like this before you rebuilt the engine?!! Chain tensioner spring might be a bit weak or the bush and/or tensioner arm itself worn or even seized up, most things available from Bill Pye at Frankfield Fantic, hope this helps

[Woody]

You don't mention ignition timing - have you checked that

[anyoldiron]

The chain tensioner on the Beta Rev 3 can be made to fit the 240.Classic Trial in Southampton are advocates of this mod and I am sure Chris of Classic Trial would talk you through the procedure.He knows Fantic extremely well-would probably see you right with the other issue if you still have a problem.I would have a look at timing too...

[bambam_n_chunx]

Thanks for the help on this, the timing was marked and rebuilt in the same position so that can be checked, I cant say how the bike ran before I rebuilt it as it was leant against a shed wall for years as the big end bearings had failed. All i`m doing is comparing it to one I used to have years ago which ran perfectly.
Could anyone let me know the correct timing setting.
Thanks

[axulsuv]

Ok ... here goes ... The timing spec is 1.6mm before tdc on the piston corresponding to 17'degrees on the flywheel ...
Or pull the timing cover and you'll see a index boss above the K.S. shaft , between a bolt hole and the flywheel. Below that you'll see the pickup with two lines on it . Now rotate the flywheel clockwise and on the edge of the flywheel will be 2 scribed lines , line up the 1st one (A) with the case boss mark and the second line should be between the two marks on the trigger body . Hope that makes sense , and the marks on the flywheel can be hard to find due to age and corrosion .
But Make sure your pipe is Clean inside . Very sensitive to exhaust restrictions . and chamber shape (DENTS).
Best of luck,
Glenn

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[bambam_n_chunx]

Thanks Glen
Will check the timing tonight, just a thought tho if the exhaust is so sensitive could an aftermarket silencer be the problem. The silencer fitted is an alloy one which is a lot larger than original and has an open area underneath the packed out part, apparently to give the pipe more back pressure and I was told this is quite a useful and sought after silencer. Probably B*****ks and the cause of my problems.

[bambam_n_chunx]

Thanks everyone who replied to my call for help.
I`ve just checked the timing and found it to be slightly out. When lining up point A with the crankcase boss the timing line was slightly outside the two marks on the pick up. Its now dead centre and the bike ticks over perfectly and picks up on the revs much cleaner. Looking forward to the weekend to give it a try.
Andy

[fantic200]

try fiting a decent rear tyre such as a michelin and a new slide for your carb, also a new fast action domino throttle might help.
hope this helps.....

[bambam_n_chunx]

Thanks fantic 200 for the sound advice, your not by anychance the nutter round the corner with the little red hair dryer??

[axulsuv]

On the carb slide ... If the slide is worn bad , than so is the carb body ... A new slide won't do much . When you get it running right , contact Classic trial and get a OKO carb kit for it , But make sure your exhaust is correct first ...
Post a photo of your silencer if you can , Sounds strange ....
Glenn

Edited by axulsuv, 25 November 2009 - 12:10 PM.