pilot jet troubles

71 Commando OE Amals

Sat for about 3 weeks and the pilot jet on the right cylinder has issues again. Why only the one side? Have been running Seafoam in it, no change so far.
Will it help to drain the bowl after every run? Wish I could ride it everyday but thats just not possible.
Any magic?

Do you park it on the sidestand?

MikeM said:

71 Commando OE Amals

Sat for about 3 weeks and the pilot jet on the right cylinder has issues again. Why only the one side? Have been running Seafoam in it, no change so far.
Will it help to drain the bowl after every run? Wish I could ride it everyday but thats just not possible.
Any magic?

Click to expand...

MM,
If you are at all mechanical then you can try here: http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html
The first diagram shows the modification for getting at the pilot jet and cleaning it out. Follow the directions below that Bushman uses to drill out the blank plug. Make sure the holes are all clear for the pilot jet in the bowl. Good luck.
Cheers,
Thomas
CNN

MikeM said:

71 Commando OE Amals

Sat for about 3 weeks and the pilot jet on the right cylinder has issues again. Why only the one side? Have been running Seafoam in it, no change so far.
Will it help to drain the bowl after every run? Wish I could ride it everyday but thats just not possible.
Any magic?

Click to expand...

could be some swarf in the fuel line getting into that carb, assuming you have the main tap on the same side of the bike, any debris would get sucked into that carb first. Scoring on the pilot jet (not uncommon when a piano wire is used to clean it out) can cause hasty build up of deposits as well. IMO, a set of premieres with the removable pilot jet is the way to go.

Or even get your carbs converted to take the premier pilot jet ,a friend of mine has his original amals on his trident converted just so he can change the pilot jet size for fine tuning ,also it makes the jet so easy to clean

Bike sits on center stand straight up.
I have read Bushmans and am able to push the guitar wire through I have external filters on the taps as well.

The main tap is on the opposite side of the issue. Just wondeing why its always the same one.

baz said:

Or even get your carbs converted to take the premier pilot jet ,a friend of mine has his original amals on his trident converted just so he can change the pilot jet size for fine tuning ,also it makes the jet so easy to clean

Click to expand...

What is the function of the pilot jet ? I've never had to change one to get the tuning right. As I understand it - it is used on two-strokes to supply fuel when the throttle is closed rapidly, to stop seizures. On any late model Amal or Mikuni, I usually use a #3 slide and adjust the needle jet and needle taper while keeping the mains slightly rich. I believe the air jet in Mikunis can be used to change the mixture right across the full range of throttle openings.
Because I always use methanol fuel, my life is much easier than for you guys using petrol.

The pilot jet bush controls the idle and low speed running

So a #78 drill bit is the best way to clean them out?

http://www.ebay.com/itm/Drill-Set-78-10 ... SwgZ1XwbNB

Is this the correct tool?

I thought the bush was the air jet and the pilot jet was the long one which screws in ? I can't remember what is fitted to my Mk2 Amals - with methanol it is irrelevant. However I can understand how someone who is racing a Trident on petrol might get advantage by leaning off the low end of the carburation.

MikeM said:

So a #78 drill bit is the best way to clean them out?

http://www.ebay.com/itm/Drill-Set-78-10 ... SwgZ1XwbNB

Is this the correct tool?

Click to expand...

You would be better off with a guitar string in my opinion ,those drill bits are quite short you may need to extend it with a small plastic tube or pin chuck to hold it

acotrel said:

I thought the bush was the air jet and the pilot jet was the long one which screws in ? I can't remember what is fitted to my Mk2 Amals - with methanol it is irrelevant. However I can understand how someone who is racing a Trident on petrol might get advantage by leaning off the low end of the carburation.

Click to expand...

You may be thinking of a monobloc they have a long screw in pilot jet

MikeM said:

71 Commando OE Amals

Sat for about 3 weeks and the pilot jet on the right cylinder has issues again. Why only the one side? Have been running Seafoam in it, no change so far.
Will it help to drain the bowl after every run? Wish I could ride it everyday but thats just not possible.
Any magic?

Click to expand...

what exactly are the symptoms that lead you to believe it's the pilot jet?

If the problem is pilot jet related it's worth checking that the whole pilot jet circuit is clear of any blockages.
On my 72 Roadster the pilot jets were clear but the two tiny holes where the fuel goes into the intake were partially blocked.
See this link to Amal info and the section on the Pilot Circuit.
http://amalcarb.co.uk/rebuilding-mark-1-concentric-carburetter
Clearing partial blockage of these holes solved the problem for me.
Regards
Andy

MikeM said:

71 Commando OE Amals

Sat for about 3 weeks and the pilot jet on the right cylinder has issues again. Why only the one side? Have been running Seafoam in it, no change so far.
Will it help to drain the bowl after every run? Wish I could ride it everyday but thats just not possible.
Any magic?

Click to expand...

The Seafoam (or Sta-Bil, or Star-Tron) will work great if used AS directed. All these fuel stabilizers are meant as a preventive measure. So, after solving this problem put it in 5 miles from home, and have no trouble.

As for Seafoam CURING any running issues, (yes, I know what the label says), it's a solvent, nothing more. Todays ethanol fuel creates corrosion in the alloy carb. Solvent does NOTHING against that. JMWO :mrgreen:

I recently had a similar problem getting the pilot circuit working on a bike that had been stored for many years.

I had cleaned everything well I thought but the bike wanted to start on one cylinder and idle poorly and no effect by turning the pilot air screw.

Repeatedly probing the pilot jet with a 0.016-inch wire/bit as discussed already did not have any effect either.

I finally got a good result by cleaning out the 'gas intake from float bowl' (described in the Bushman's site) passage to the pilot jet.

The old (1968?) Amals originally had the pilot jet screwed into the bottom of the carb body. This is the point where fuel is sucked up and drawn into the pilot jet/mixing chamber. If there is an obstruction at this point there won't be fuel mixed properly for starting and idling.

Here is how I blew it out with the carbs still on the bike: Plug the air intake (blue plug), find a suitable rubber grommet to slip on the straw from your carb cleaner can so you can force the spray out of the fuel pick up hole (red painted hole). You should see a good spray coming out of that former pilot jet hole. Place a clean tray underneath to catch the spray to see if any debris comes out. I can imagine that bits from the float bowl gasket could end up in there. I think someone had installed a bushing at that point to try to improve the seal between the float bowl and carb body.

Also shown in my photo is the pilot jet probe with drill bit. The probe will go in 1.5-inch to bottom out in the body.

acadian said:

MikeM said:

71 Commando OE Amals

Sat for about 3 weeks and the pilot jet on the right cylinder has issues again. Why only the one side? Have been running Seafoam in it, no change so far.
Will it help to drain the bowl after every run? Wish I could ride it everyday but thats just not possible.
Any magic?

Click to expand...

what exactly are the symptoms that lead you to believe it's the pilot jet?

Click to expand...

Dead cylinder on startup right side. Finally got it to work and has an erractic idle plus I took it to the shop that built and tuned the engine and he cleaned the pilot jet on the right cylinder. Runs fine now. BTW anyone ever break off one of those tiny drill bits inside the carb, just wondering.

Just to stir the pot .... my Mikuni has been trouble free for , let's see , can't remember last time I had issues with that carb ..... I've had it in service for 10+ years I'm thinking ...