Idle dont goes under 2000 mph

I had many ignition troubles since the bike was rebuild, (kicking back, advanced timing...fast idling...)
I do believe the Boyer ignition doesn't work well as expected...
Is it possible that the ignition timing, well settled with a strobo just a couple of months ago change so soon?

I'm thinking to try a Pazon...

But for sure I will check more closely the carbs body and how slides works
I'll be back soon with some pics or video
if I won't be able to solve this idling problem I will soon try a Pazon
Mario

Thomas, it may not be related to your fast idle problem but I would blend your 30mm manifolds out to 32 to make a smooth transition at the carb to manifold connection.
Jaydee

I'm not sure the plate moved from the correct position,
I will check timing but also if the battery is too low...
maybe low battery and poor sparks could be the reason of the back fire...

A low battery will cause kickback with a Boyer ignition..I had the same high idle problem with a 750...After checking all possible ideas I took air cleaner off and pushed against the slides and the idle lowered...The worn slides were causing the high idle problem and after getting them sleeved the bike idles perfectly...

Thomasdunstall said:

Dances with Shrapnel said:

AntrimMan said:

If you have AAU and points the AAU may not be retarding sufficiently to lower the idle.
All the best.

Click to expand...

+1 what he says.

The Automatic Advance Unit (AAU) is notorious for stick the ignition in the full advance. This is the most typical cause for a high idle. See if you can confirm the AAU is free to move and spray a little lubricant in there......assuming you still have points.

Click to expand...

Hi,
I don't have points,
I have a Boyer Bransden e-ignition fitted on the bike,

since the bike was just rebuild I had kick back problems,
It was a bit advanced,
working on the ignition plate and using a strobo the problem has been solved,
but, yesterday the bike was again a bit advanced and gave me some kick back,

Idle still too high 2.000 rpm since the bike was rebuild, no way to lower it,

Do you think it could possibile I have a problem with the e ignition?
May be it doesn't work correctly?
I could try to fit another e ignition...
Thanks
Mario

Click to expand...

An advanced ignition will give you a high idle. If it was set correctly and is now advanced, this may likely explain your high idle.

To the best of my knowledge, a Boyer does not "slip" electronically with a good battery. If the trigger plate has not slipped then take a look at the rotor which bolts into a taper fit on the end of the cam shaft. Is there any hint of it being loose?

Also worth looking at the alternator rotor which you rely on for the ignition timing mark. These rotor have been known to loosen such that you may think your ignition is set correctly. See if there is any indication of fretting between the steel collar and pot metal of the alternator rotor; if it looks tight and feels tight then this is probably not an issue.

Here is another possibility.....

Sometimes when replacing the slide/spring/needle combo the needle and clip wind their way upwards on the spring resulting in your mixture being a mile off in one carb. Very difficult to see unless you take off the carb top and remove the innards for a look-see. But it happens quite easily

Nothing wrong with the Pazon if you want to try it. Happy with mine.

What sealant do you use between head, insulator and manifold?
Manifolds have not a flat surfaces,
I need to grinding them to flatten the surfaces,
just to avoid air leaking
and I was thinking to use also a sealant between head and insulator and between insulator and manifold,
Any suggestion?
Many thanks

No problem with slides and cables,
Idling problems not related with them, i believe,
More probably an air leaking problem?
Mario

Thomasdunstall said:

Manifolds have not a flat surfaces,
I need to grinding them to flatten the surfaces,
just to avoid air leaking
and I was thinking to use also a sealant between head and insulator and between insulator and manifold,
Any suggestion?

Click to expand...

Use flange gaskets on both sides of the insulators instead of sealant?

http://www.rgmnorton.co.uk/buy/carb-man ... m_4095.htm

I'll buy this LAB many thanks,
do you think it works fine, better than sealant?
Mario

Thomasdunstall said:

do you think it works fine, better than sealant?

Click to expand...

Yes, I would think so.

It gives a heat break . quite important.

Have seen this happen when the original plastic throttle cable "Y connector" (2 cables to 1 cable) has been replaced. Sometimes they are not made correctly internally and the cables are still holding up the slides.

Russ

My 750 has the early model center mounted oil tank and I use a K&N washable air filter, so I can remove the air filter and visually inspect the carb's slides by removing the seat and looking forward to see if the slides are dropping all the way down with the bike running. It sounds like your slides arent going all the way down... You should check your needle position and see if it's in the middle slot,... and check that your needle clip hasn't been displaced from under the spring upon assembly. (which is easy to do)

If your slide bodies are all the way down and your idle is 2000 rpm, I would try moving the needle down just to see if it has any effect, but I wouldn't bet on that being your problem.

Are both exhaust pipes hot?? Start the bike, run it at 2000 rpm's and spit on the exhaust pipes, did they both smoke when the spit hit the pipe? If one seems cooler than the other, you could have a misfire on one side and not realize it, so your bike is actually pumping warm air on one side and firing on the other. My bike did this and I thought both cylinders were firing because of the blast of warm air out of both pipes, but one cylinder actually wasn't firing. I could actually get my bike to idle at about 1100 rpms on one cylinder, so I assumed they were both firing.

If you are really just running on one cylinder at idle, but have plenty of power when you lift the throttle, that means the 2nd cylinder is kicking in at some point, which points to idle jet issues... This was my issue recently, and I had all kinds of backfiring, misfiring, and popping in the exhaust on the misfire side which was related to the bike going in and out of the RPM range where the carb cut off the fuel because of the plugged idle circuit.

I hate to sound like a broken record... but idle issues seem to be mostly carb idle circuit related. A boyer doesn't have an Auto Advance unit that could stick in the advanced postion like a points ignition, so I am betting it's a carb issue. After I fixed my idle circuit issue, my bike idles better than it ever did, leading me to believe that I had a partial blockage in the idle circuit for a very long time... and didn't actually know why other nortons with the same carbs idled so much better than my bike...

Hi mario/piero.
Still having problems?
Disconnect the throttle cables at the slides then re-assemble the slides, needles, springs and caps as normal (making sure the slides are pushed all the way down and the caps are sealed). Do not install start-up chokes. Screw the idle airscrews out 1and 1/2 turns (540°) from fully seated and screw the throttle slide stop screws 1 complete turn (360°) in from first contact.
Start the bike. If it starts and idles ok then the problem is in the cables.
If it won't start, ensure the pilot bush and especially the two pinholes are clear in each carby.
If it starts and runs fast, suspect air leaks.
Ta.

o0norton0o said:

A boyer doesn't have an Auto Advance unit that could stick in the advanced postion like a points ignition,

Click to expand...

A boyer with low battery voltage will go to full advance, with no retard function, so this cannot be entirely ruled out ?
Although I wouldn't argue with the importance of having clean and unobstructed idle passages.

Hi,
I've removed and serviced carbs,
cleaned all,
flatten manifolds,
check once more cables,
all seems ok,
only issue I found very irregular surfaces on manifolds (head port side)
problem solved,
I will get the carbs on the bike,
I hope it was just an air leak problem or checked idle circuit...
I'll be back with news soon...
Many thanks
Mario

Worn slides???

Slides are new, maybe ovalized bodies...
I'll try tomorrow
We'll see what happens
Cheers
Mario

I always make sure that the flat surfaces are truly flat on the carb flange and the manifold flanges. The usual sandpaper and glass.

AS FOR GASKETS..... I throw away the large Oring in the carb flange. Grey Yamabond and a paper gasket work great. Tighten the mounting bolts just snug while constantly turning the throttle to make sure the slide bore is not warping. The yamabond will GLUE the two surfaces together so high pressure is not needed. As for the manifold...I THROW AWAY the phenolic spacer, opting for the much more useful 1/8" thick paper gasket which must be special ordered. The reason here is that phenolic will not cling to Yamabond and the other one will, making for an AIRTIGHT SEAL...The proof is when you dismantle these gaskets, the paper one is glued on so well that it tears in half while the phenolic will have no trace of yamabond....it got sucked into the motor....and you have an unregulated air leak. Both make good insulators. I know this will bring arguments but it works well everytime. Forget the phenolic.

Interestingly enough, the carb can be tuned even with the air leaking past the phenolic...It will be about the same on both carbs...I recently fattened the needle jet to a 107 with very good results on a friends bike because he was running the phenolic spacers.