My Weekend

[robjameson]

So, with all this wonderful weather, and generous donations to the motorbike fund for my birthday, I finally bought a new carb, and had it delivered for saturday morning so i could get it fitted and try it out this weekend. (went for the 376 with a 220 main jet re: previous topic - both amal and surrey cycles recommended that I DON'T use a concentric). I've just finished fitting steel flywheels and an HS camshaft so i was looking forward to how the bike would be.

I'll list what went wrong:

Saturday

1. timed it on the wrong stroke (schoolboy error - i was being lazy)
2. Completely lost spark (mag refurbed professionally 5-600 miles ago)

Eventually got it started and running lovely, even returning oil (which it had stopped doing before the rebuild)

Sunday

Went out for a ride.

1. Bike ran incredibly hot
2. No top end power

Came Home

1. Oil cold. Not returning - hopefully not knackered engine as i poured a decent amount of oil in to the bottom end
2. Spark has left the building
3. spark plug core broken (second one in less than 100 miles - i don't recommend NGK)
4. Gearchange indicator was loose, so i went to tighten, sheared right off - new gear selector cam needed
5. Rocker oil feed pipe cracked.

As you may understand, my language has been 'colourful' and i have even got to the stage of threatening to trade it in... I never will though.

So, if i am very lucky, I might get it to work in time for the Annual in Market Drayton next year!

[Steven.Carter]

wow. that's a lot wrong. you must get to the bottom of the oil problems first. hope things improve for you.

[chris jane]

Hi Rob sounds like the perfect weekend messing with the bike as the old man keeps telling me it takes years to get them just right,just been out for the first time on my 500, it seems after adjusting the chain tension i forgot to tighten the brake steady bar, the bolt fell out ,on pressing the brake pedel the brake spun around on to the swinging arm locking up the back wheel lots of fun in the middle of the road ,plus the bike trying to cut out when you give it some welly, bike back on the bench again

[brenton.roy]

Hi Rob, it seems to me that each 'warm' engine is unique for carb settings. Other factors come into play.
This drags article is pretty good. http://www.draganfly.co.uk/data/pdf/Amaltype6tuning.pdf
Sounds like it is lean. Particularly if it is cooking the porcelain at the tip of the electrode. To save money, try to find someone with a jet kit, or buy in two size increments.
Good luck with the repairs.

[john.nash]

3. spark plug core broken (second one in less than 100 miles - i don't recommend NGK)
!

My experience of NGK is that they don't tolerate very rich conditions for very long and become unusable.
I'd suspect your carb and ignition problems are killing your plugs ..

Sounds lean to me too.
You can confim that by riding along and lowering the choke slide (via the lever) this will cut down on the amount of air that can get in and richen the mixture.
If things get better then you need bigger jets. You can change the main jet without removing the carburettor.

[ian.scott]

The main jet only comes into action on the very last 1/8th of the travel , providing it is not ridiculously small ,far more likely is the throttle slide/ needle position or even the wrong needle.

Ian

[john.nash]

The main jet only comes into action on the very last 1/8th of the travel , providing it is not ridiculously small ,far more likely is the throttle slide/ needle position or even the wrong needle.

Ian

I am going to dare to disagree.
The main jet seems to have a surprisingly noticable effect at other throttle openings (on the amals at any rate).
I know we've discussed this before, on the forum.

[robjameson]

So far, I have replaced the magneto pick up and noticed a significant improvement to the strength of the spark, so I think the old one is duff.

My theory is needle needs moving up a notch, and I think it has been retarded before the mag pick up change, causing the overheating and lack of power.

I will keep you all informed of any progress.

Thanks so far!

[brenton.roy]

Hi Rob, good to read that the pickup might solve your mag problems. With some luck, you'll be out riding sooner than you thought.
Re the jetting, John's point about the main jet affecting across throttle settings is worth considering. I posted this link to Drags a little while ago. While it refers to an earlier Amal, the theory is the same. It suggests tuning the main first, the needle last. http://www.draganfly.co.uk/data/pdf/Amaltype6tuning.pdf
I've just spent a bit of time tuning to a HS style cam. Even when I thought I had it right, I found I was slightly lean - by accelerating up a hill in top gear. I was lucky not to do major damage.
The bike ran perfectly across the other 9/10 of the rev range.
So, at the risk of sounding like your mother.. Maybe go up one size main. An error in needle position will be annoying. An error in main can be terminal.

Regrind cams are often slightly diferent to the original. The cam I have spits back at idle and is a bit dead at low revs. David Anderson has a couple of later VH's that perform quite differently with the same HS style cam. The difference is likely the way the heads flow. My point is that the jetting for each of these bikes will likely be different. I'd be wary of trusting any set jetting data, from Amal or otherwise.
Brenton

[nevhunter]

With the air slide fitted, lowering it will show if the motor is lean as it will improve straight away as soon as you lower it even slightly. With it right down of course you will lose power because it obstructs airflow. IF the flow to the bowl from the tank is the cause this will not work. Nev