uneven idle

yasser_fernandez · Jul 16, 2013

Can anybody enjoy of a super steady (japanese like) idle on your motorcycles with a dual carb set up and a Boyer Bransdem electronic?

concours · Jul 16, 2013

yasser_fernandez said:
Can anybody enjoy of a super steady (japanese like) idle on your motorcycles with a dual carb set up and a Boyer Bransdem electronic?

I'm pretty pleased with mine, Boyer/old (19,000 mile) Amal's

DogT · Jul 16, 2013

Good idle is probably more an issue of good ignition and carb setup than just the ignition system. I've heard some real nice idling in youtubes here. Coming up to a stop and just going into a nice stable idle, I've seen it on the Norton here.

ashman · Jul 16, 2013

I have never had any problems with idling and boyer system even with worn out slides in my Amals it still idled good (2sets of amals, 1 lucas and 2 boyer systems) I am now running a Joe Hunt maggie and Jims Flatslide carbies, this so far has been the best set up of all, but my Norton has always idled good from new, just don't let it idle to low.

Ashley

bmwbob · Jul 16, 2013

Old Boyer electronic ignition doesn't like low voltage making for rough idle! Go for a spirited ride and mine would idle great. Ride around town at low revs and idle deteriorated. Current tech electronic ignition require less juice and all is well around town.

chilly · Jul 17, 2013

My mates Mk 3 wouldn't run very well at all on Iridium plugs , put in some Champion N3s and all is well

yasser_fernandez · Jul 17, 2013

Thanks all posters for replying a topic that, at first sight, seem a little bit foolish. I’ll try now to explain deeper for you all of you to understand my complains.
I have a Boyer with a healthy battery fitted; I use Bosh Platinum Plugs actually with a very good reading. Period in this matter.
A dual manifold fitted, with a couple of pekar k68 carburetors in good condition, and before this setup I have tried, ikov, amals, dellorto’s and so.
Results? The motorcycle idles decently at aprox 600RPM. But, and that’s my dude. The engines makes putún, putún, putún pururu, putún, pururún….instead of a steady putún, putún, putún, putún, putún constant in time…
Why? Is that normal? Why after three strokes it “looses it rhythm”.
You can assume that valves, timing and everything else is in good condition.
I have open pipes fitted.

Nortiboy · Jul 17, 2013

yasser_fernandez said:
Why? Is that normal? Why after three strokes it “looses it rhythm”.

I have open pipes fitted.

If you have open pipes, you may need to look at the idle mixture. 600rpm is probably too low. Try increasing the idle speed. Even 1000 plus will be better for cam life.

I had a Boyer. Changed to Trispark and idle was much better.

concours · Jul 17, 2013

Ikov? Pekar? I've not seen these brands, are these resellers of other brands?

Edited... Found the Pekars, Russian?

yasser_fernandez · Jul 17, 2013

MMMM.....well I forgot to mention I live in Cuba...Those are trademarks of JAWA (a czech motorcycle) and URAL (a Russian one).

But they are good carbs, not as good as Mikuni but the do their job. :|

concours · Jul 17, 2013

yasser_fernandez said:
MMMM.....well I forgot to mention I live in Cuba...Those are trademarks of JAWA (a czech motorcycle) and URAL (a Russian one).

But they are good carbs, not as good as Mikuni but the do their job. :|

Cool... It's a good day when I can learn :mrgreen:

ML · Jul 17, 2013

yasser_fernandez said:
MMMM.....well I forgot to mention I live in Cuba...Those are trademarks of JAWA (a czech motorcycle) and URAL (a Russian one).

But they are good carbs, not as good as Mikuni but the do their job. :|

You may have to check if the JAWA and URAL carbs are from a 2 stroke model. The idle jetting and needle jet & spray tube can be different to a 4 stroke version.

yasser_fernandez · Jul 18, 2013

mmmm…open pipes 1000 plus! The domi roar is louder enough to turn me crazy at that idle RPM!!!
And yes, I agree with you, just pulling a little bit the throttle this steady tick over arrives..
Unfortunately I don’t have the opportunity to acquire a Trispark..
Two stroke carbs…? Yes you are right JAWA is a two stroke but not URAL, is like a kind of BMW Russian copy, and those are the dual carbs I have fitted.
Let me share a comment I found on the internet that seems to photograph the exact problem I am having.

"A worn carburettor can completely spoil the most meticulous of engine renovations and will lead to increased petrol consumption. Its effect is most noticeable at low engine speed and whilst idling. Many people have never experienced the tickover of clockwork regularity that can be obtained with an instrument in good condition, simply because most used machines do not have an instrument in an acceptable state., To function efficiently a carburettor must have a well-fitting slide in a truly cylindrical bore. This is impossible in a carburettor that has done a significant mileage. Just fitting a new slide is of little use, since it is made to the size that the carburettor used to be and, in any case, the old slide may well fit the carburettor better at the forward (ie, engine) side since it has spent most of its time rubbing against it. Very little wear occurs on the atmosphere side of the carburettor bore, because the slide is always pulled forward by the induction depression of the engine and it rarely contacts the atmosphere side".

My slides have actually free play inside the carb body…even when the have less than a year of use.
So, as is very difficult for me to resleeve the slides I am asking for ideas to fix this, with home mechanics.
I am thinking in fitting a small Teflon line in the slide guide groove upper part..this will provide some pressure to the slide against the carb body and maybe eliminates the free play!
Opinions?

Bernhard · Jul 18, 2013

yasser_fernandez said:
mmmm…open pipes 1000 plus! The domi roar is louder enough to turn me crazy at that idle RPM!!!
And yes, I agree with you, just pulling a little bit the throttle this steady tick over arrives..
Unfortunately I don’t have the opportunity to acquire a Trispark..
Two stroke carbs…? Yes you are right JAWA is a two stroke but not URAL, is like a kind of BMW Russian copy, and those are the dual carbs I have fitted.
Let me share a comment I found on the internet that seems to photograph the exact problem I am having.
"A worn carburettor can completely spoil the most meticulous of engine renovations and will lead to increased petrol consumption. Its effect is most noticeable at low engine speed and whilst idling. Many people have never experienced the tickover of clockwork regularity that can be obtained with an instrument in good condition, simply because most used machines do not have an instrument in an acceptable state., To function efficiently a carburettor must have a well-fitting slide in a truly cylindrical bore. This is impossible in a carburettor that has done a significant mileage. Just fitting a new slide is of little use, since it is made to the size that the carburettor used to be and, in any case, the old slide may well fit the carburettor better at the forward (ie, engine) side since it has spent most of its time rubbing against it. Very little wear occurs on the atmosphere side of the carburettor bore, because the slide is always pulled forward by the induction depression of the engine and it rarely contacts the atmosphere side".

My slides have actually free play inside the carb body…even when the have less than a year of use.
So, as is very difficult for me to resleeve the slides I am asking for ideas to fix this, with home mechanics.
I am thinking in fitting a small Teflon line in the slide guide groove upper part..this will provide some pressure to the slide against the carb body and maybe eliminates the free play! Opinions?

You might be better off in the long run to get the slides ground down absolutely true and getting the slides Teflon coated. I have standard slides in my Yamaha LC350 that are Teflon coated.

yasser_fernandez · Jul 18, 2013

sorry can you tell this again in a more basic english?

Is there a way I could cover mines with teflon?

Maybe meltin some tetlon and inserting the slide in?

Hobot · Jul 18, 2013

When I did not know what made my idle too high or stalled dead I put grease on my worn slide that gave back idle control for a few days before the grease washed away. New Anodized Amal slides with one number lower slide cut out to make up for the carb bore wear bigger. When idle again stayed too high it turned out to be the worn mechanical advance due to wear in the moving parts but also the springs stretched out too much. The Chevy points springs are too long to substitute.

yasser_fernandez · Jul 19, 2013

Cool! I will try some grease on the slide...at least to know if my trouble at this point.

Bernhard · Jul 20, 2013

yasser_fernandez said:
sorry can you tell this again in a more basic english?

Is there a way I could cover mines with teflon?

Maybe meltin some tetlon and inserting the slide in?

Sorry but I really don't know how Yamaha do it.

All I can tell you is that is how they come over the counter /in the bike, as standard.
So it must be possible to coat the slides with Teflon, provided you have enough clearance in the carb body to do it.

yasser_fernandez · Jul 23, 2013

Yesterday I did a small trick suggested by a friend. Put some grease in the slides and start the machine. It does work better...

So I am having problems with the slides on my carbs.

Hobot · Jul 23, 2013

Amal slides and bores get beat up and ground down from both the engine vibes and the inhaling pulses till air gap too wide and worn to a fluted grooved condition > no known recovery from w/o new items. My new set of 32 mm Amals only lasted about 7000 miles before flutes and fast idle appeared. Don't know of a coating that would last long but sure temped to try some layers of baked on paint that gas don't dissolve. If painted faked off no big deal its soft and combustable so nothing bad to try it but maybe the slide sticking open so need kill button to save. Carb body bores can get out of round too so might try light tapping around slide bore with slide inside to crimp tighter, for a while. My long term solution was the new anodized hardened slides with one number lower cut out, ie: #3.5 to a #3 to help compensate for the worn bores and it did, plus a bit more low throttle response to boot. In the rest of the world we can send carbs to be resleeved with new hardened surfaced slides that apparently solves for decades. The zinc pot metal is poor to have chrome plated or over metals as was found out the hard way by engines inhaling the big flakes to chew up and spit out.

uneven idle

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