Fine tuning ?

[straycat]

Finally got the Tank cleaned again. Looks a lot better.

I have a Motad 4-1 system which I bought 2nd hand. I had a spare set of jets 2 sizes up from standard,so I fitted them today and the tank (with an in-line filter to observe any residual rust or muck).

Bike started well and was soon off choke and idles well. Took her out for a quick run tonight . Pulls a lot stronger with new main jets and when cold, pulled really well at all throttle openings,then I got it hot...........

It seems to hesitate / cough at about 2.8k to 4 k at 1/4 to 3/4 throttle. I seem to be able to get through it either at a small throttle opening or if I wind it fully open at 2k it can get to 4 k without a blip .
As this got worst as the bike got hot, I assume this is a rich problem ?
Is the needle position critical to this area? I checked them when I had the carbs in bits and they are at 3rd position with no noticable wear.

bike finally idles when hot or cold.

sc

[Steve]

It seems to hesitate / cough at about 2.8k to 4 k at 1/4 to 3/4 throttle. ...

Is the needle position critical to this area? I checked them when I had the carbs in bits and they are at 3rd position with no noticable wear.

Yep, that's where the needles are doing "their thing".
Since you are blessed with adjustable needles , lower the clip one notch to raise the needle, then try another run or three.

.

[hampshirehog]

Steve is right about this throttle setting being in the needle circuit but as you appear to be running rich on the midrange it's the other way round - i.e. raise the the clip on the needle (so that the needle sits lower).

I am surprised that she's running well at the top end with bigger mains. Motads are a very 'benign' exhaust and I've never had to change a thing in the carbs when fitting one (apart from the odd tweak on whatever screws control the idle circuit).

[straycat]

I agree about the Motads,but from what I've read the general rule seems to be 2 sizes up for a 4-1 aftermarket and another 2 sizes if using pods.It may just be pulling stronger because everything is now clear in the carbs (?)

It was doing this hesitating with standard jets before I rebuilt the carbs,so changing the mains hasn't caused it. I'm going to experiment today.

[straycat]

I managed to get the carbs balanced and attempted to set the pilot screws by the highest rpm method,which ended up 2 1/2 turns out. It's actually worst now. Lumpy right off the stop ,almost to full throttle although it clears at about 4 1/2 K.

I haven't touched the needles yet as something is bugging me -

Why is it running rich ? ;

Floats are 22.4 mm exactly

Mains are 2 sizes up,but it behaved the same with stock

Needles are at position 3 as stock

I very much doubt a 4-1 exhaust would make it run rich . It would normally be a little leaner.

I cleaned and lightly oiled the air filter

why dosen't it misbehave above 4200 RPM at any throttle positions.

COULD IT BE ELECTRICAL ? The bike became a very poor starter last winter when I wanted to occationally start it,sometimes needing 3 battery charges to get it to fire up.

TODAY:
I tested voltage at coils and it is 10volts. Battery is giving out 12.4 ish volts. I have run a temporary lead from battery to coils to get 11.2volts and test rode the bike NO IMPROVEMENT. I noticed when I connect the coils the Battery voltage drops by approx. 1 volt and I can see some sort of load arching as I connect cable - is that normal ?

I know this should probably be on electrical topic ,but I'm trying to keep it together !

sc

[straycat]

Am I going down the wrong road with the carbs ? AND if it's a rich peoblem,why did it get worst when I "leaned off" the pilot screws ?

My head's everywhere with this and........................................my wife is now "sick of it" !

sc uk