Hi guys,

Just bought a 1979/80 198 A 250, it has electronic ignition.

I've bought a new spark plug which I've been advised needs a gap of 0.4mm, but when I ordered it I didn't say it had electronic ignition. Is there a different gap setting for each.

Also the bike runs and starts well on choke but dies when the choke is turned off.

I've had the carb apart and found

150 main jet.

20 pilot jet.

3 slide.

2b1 needle

106 main jet.

I've had carb cleaner through each and every orifice, because I thought it would have been a blocked pilot jet.

The previous owner has owned it for years but hasn't really used it for a few years.

I've drained and flushed the tank and got new fuel mix at 50:1 with synthetic oil.

But it runs fine on choke and then dies.

Am I missing something obvious ??????

Many thanks.

Checked carburettor rubber union for leaks/properly tightened? Could bind with insulation tape as a quick fix to check if this makes a difference.

So it runs when it's rich (I.e. With choke on) - agree with cleanorbust sounds like an air leak..

Thanks , with it being stood for so long it may be the crank seals that have failed, or at least the flywheel one as it's not smoking.

I'll start looking for an air leak.

Any views on the plug gap for electronic ignition, or is it the same as standard?

Hi Chappo, before you start pulling it apart to do the seals, are you absolutely sure that the jets are clear? Sometimes they need a careful poke with thin wire to clear an obstruction.

electronic ignition supplier should tell you what gap to use, but there will be no harm done using 0.4mm. I use 1.0mm plug gap on my bikes that have modern aftermarket electronic ignitions.

The recommended plug gap for the CDI on my Sherpa is 0.7mm. This is the one from a well known English Bultaco shop. Graham.

I would go along with 0.7, any larger and you are more likely to get a spark on the outside of the HT lead or HT coil when its wet. Electric takes path of least resistance

Hi Chappo, I imagine it has an Amal carb??

What you are describing is a blocked pilot as Pigbog mentions, I am no help when it comes to 

Amals but if you have access to another carb???

As to seals; very unlikely in my experience.

 Have a nice day

Larry

 

 

 

 

Thanks gentlemen,

That gap info is great, not taken the flywheel cover off yet so not sure of the manufacturer.

Larry, yes my mistake it is an Amal 2600 series 2 concentric.

Ordered a new float and associated jets, the jets that Amal have on their records as being correct for the bike are the ones that are in.

Going to have it sonically cleaned then fit the new jets and go from there.

Will update with progress later in the week.

Regards, Dave.

Hy Chappo

I think the slow jet 20 is wrong, should be about 42 or 45. Would explain, why it only runs with the choke.

New jets are always to recommend. Make sure ab out the original size, can maybe deviate 1 number, if different air box is fitted.

 

don't think the 4 or 7mm makes a big difference, but 4mm seems to be good (used on my Sherpa M49 250cc with new electronic ignition)

 

good luck, Pat

The jets you have listed are correct for an amal on a 198A. Amals are notorious for wearing out the slide and the needle '2B1' and the needle jet '106'. The bike will start easily and run ok until you try to rev the bike then it will splutter and carry on a treat. No amount of messing with the mixture screw or moving the needle will fix it.I am not sure this is what yours is doing but the needle and needle jet should be replaced before you do anything.

Thanks Sherpa 325.

Mine starts a treat runs smoothly on choke, but not that fast, you then turn the choke off and it dies.

New needle and full set of jets on order.

Thank you.

Throw the Amal carb in the bin and replace with a new mikuni carb is a good way to go i really wouldn't bother wasting money on new jets. on a old tired Amal carb.

Thanks Bondy,

Seen your Sherpas on here, is that what you have on yours, the Mikuni replacements?

Jets have arrived today, just want to try and get it ready for a first outing this Saturday.

After that I'll look at the Mikuni options.

Edited November 3, 201510 yr by chappo