KH running badly

[Henrik Ravin]

Hello! My 1954 KH twin is a first kick starter and idles as it should, but when I open the throttle above 1/4 it begins to hesitate run bad and sometimes backfires. Last season there were nothing like this and I haven't changed a bit. Any ideas?

IMG_4674.mov

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[simon.holyfield]

Excuse my ignorance - I don't have a KH - but is the AR unit stuck?

Alternatively, has your needle and jet become very worn?

And lastly - not a joke, I have done this much to my own embarrassment - has your main jet fallen out?

[Henrik Ravin]

The needle jet, main jet and needle was new last year, they worked flawless then. The main jet is fitted, I took everything apart and checked för dirt.
Is the AR the ignition timing advance unit?

[Mick D]

Hi

Yes, check that it's free to move, wash out with petrol and oil sparingly.

Regards Mick

[Henrik Ravin]

Thanks! The contact breaker plate can move back and forth a bit. Do i need to disassembly more than the cover for cleaning and inspection? The leaf spring is broken, I only found out now, when I saw pictures of how it is supposed to look, it has probably never been there since i bought the bike.

[chris.shearwood]

I just listened to the recording in your first post and while I know next to nothing about the KH I am wondering if you don't have the choke completely closed. If not, perhaps this trouble shooting page from Nicholson's book will lead you in the right direction.

[nevhunter]

A piece is missing where you've circled and the Moving Point can then move sideways on the pin it Pivots on.. Nev

[Mick D]

Hi

The advance/retard unit is on the other end of the magneto, inside the timing side cover.

https://draganfly.co.uk/shop/83182/auto ... #K151Z-48F

Go back one screen to see where in the overview.

Regards Mick

[Chris Sealy]

It should not be possible to move the contact breaker assembly. It should be firmly fixed by the central screw. I can see what looks like a piece of copper shim between the central screw and the hole in the brass, which should not be there. The screw should be tapered to match a tapered hole in the brass piece.
There is more wrong with your contact breaker assembly than a broken spring and a missing piece of insulation. I think that you need to fix this before looking for other problems.
Cheers, Chris.

[Roger Gwynn]

The whole CB assembly should be able to be rotated a little along with the advance/retard mechanism. The movement you describe is it up and down (worn bearings or missing insulation washers), or in and out (similar cause) or rotate more than the movement of the adv/retard mechanism?