Flat spot M35TP

Need help to tune my carb

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Flat spot M35TP


Post by bavarian_knuckle » Thu Sep 06, 2018 7:01 pm

Hi guys,

I am new here in this forum. Spend a couple of years at the S&S Techtalk but it seems that the traffic over there is getting less and less. I live in Germany and also spend some time in the year in Canada, Quebec. I have a staple of bikes, mainly old Harleys and Beemers, which keep me quite busy.

Here's the thing. My Knuck (M35TP Linkert with PEEK rings) runs ok but does have a flat spot around 2000 revs (I would say). When I am in that position, the bike just doesn't want to accelerate, actually almost stalls. Once I further twist the throttle, all is good ... the biest pulls.

Now, I think I have a little air leak at the rear cylinder which I only could check with carb cleaner so far (PEEK rings are about 10 years old now). Once I spray A LOT of carb cleaner on rear manifold connection, the revs go down but the engine doesn't stall. So, yes, I will do the vacuum test in the coming days. Front plug is blackblack powder ... the rear one is nicely taned. However, carb adjustment seems to be on the lean side: Speed needle is 1,5 turns (sounds about right) and idle needle also at 1,5 turns (which seems to be on the lean side ...). Bike starts fine

the bike doesn't smoke

Funny thing, I measured the temperature right after a nice country road ride (between 40 and 60 mph for an hour-ish). Apologize for the Celsius measurement: Both cylinders and heads are almost the same temperature. I measured the cylinders (125 Celsius) and the heads (160 Celsius) and also the aluminium knuckles on the right side of the bike (55 Celsius).

Otherwise the biest is all stock only running an electronic ignition which is spot on.

any ideas?


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Re: Flat spot M35TP


Post by 1950Panhead » Fri Sep 07, 2018 1:22 pm

Front plug is blackblack powder ... the rear one is nicely taned
Fix your leaks then adjust your needles, I start at low=3.5 high=1.0

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