McCulloch 1-40 Tillotson HL 63A questions

[spudulike]

I have acquired on of these vintage machines, seems good condition all round but have a running issue despite fitting a new carb kit, fuel lines and timing it. The saw also has new crank seals, have lowered the cylinder gasket and got the compression up to around 180 and used a timing wheel to set the ignition to 28 deg BTDC.

The issues are, apart from making my ears bleed, the saw runs in pulses of around three beats, goes quit then bang, another three fires and then silent. I have had it going flat out but sounds like it is strangled, idle is pretty ropey as well, and if it will run on a fast idle, it eventually dies. The spark is very strong but cant be 100% sure the coil is perfect but the spark says it is.

So, I pulled the welch plugs in the Tilly carb HL 63A and under what I thought was the high speed check valve was a brass tube which the high speed screw fits in to. The low speed fuel is pulled in via a small hole near this hole and goes around this tube under the welch plug and is fed in to the low speed circuit.

The high speed fuel is pulled in under the metering arm, fed in to where the H screw sits and then goes straight in to the high speed nozzle.

I have tested for a check valve on the High speed circuit but there appears to be none as you can plug the fuel inlet, attach a tube to the high speed screw hole and suck and blow with no restrictions.

Are these early Tillys like this? First time I have worked on anything so old and TBH, it has me stumped and it is damn rare whan this happens.

Images to help you - first one is the carb WITH the plugs pulled.

 

[alexcagle]

I'm not positive, but isn't there a check and screen under the little plug by the other HS welch plug?
If not, pm @backhoelover

 

[Chainsaw Jim]

It sounds like you have the timing so far off that it can't run right. Is there not a flywheel key to line the flywheel up?
I don't know if this information is helpful or not but I'll go ahead and upload the screen grab anyways.

 

[spudulike]

I'm not positive, but isn't there a check and screen under the little plug by the other HS welch plug?
If not, pm @backhoelover

I am guessing you mean the small brass plug above the welch plug that isn't the low speed one - I was thinking that but there is no sign of any valve action as if you block the fuel pickup and suck and blow on a tube stuck in the H screw hole, there is no sign of any seal at all - an ultrasonic clean, carb cleaner etc has done nothing

 

[spudulike]

It sounds like you have the timing so far off that it can't run right. Is there not a flywheel key to line the flywheel up?
I don't know if this information is helpful or not but I'll go ahead and upload the screen grab anyways.

There is a key (service tool) but I think I may have more luck finding the Holy Grail, the saw was running bad before I timed it and then stripped it and retimed it with a timing wheel giving it 28 degrees advance rather than the standard 26 degrees. it doesn't backfire and kicks back every now and then so don't think it is out but will check again.

I port saws so am no novice to using a timing wheel and setting points.....just saying )

 

[Chainsaw Jim]

I port saws so am no novice to using a timing wheel and setting points.....just saying )

I gathered that by the comment you made about using a degree wheel and setting the timing, but that doesn't mean you're good at it. Lol.....just saying.

So if it isn't the timing then possibly the ignition.

 

[backhoelover]

i have the tool to do the timing

 

[backhoelover]

cant remember the guy name that gave them to me, thats right gave them to me. he is a big mcculloch collector . i have the hl service manual but i will have to email it to you.

 

[backhoelover]

i also have the service manual just send me your email address

 

[spudulike]

I gathered that by the comment you made about using a degree wheel and setting the timing, but that doesn't mean you're good at it. Lol.....just saying.

So if it isn't the timing then possibly the ignition.

Don't worry, not having a go, I appreciate all input, I found TDC using a piston stop and rotating the timing wheel back and forth and then made sure the points opened at bang on 28 degrees, a little more than standard but that's the life of a tuner, may just knock it back to 25 deg to make sure but it shows no signs of that rumble you get with too much advance - been there before but not with this project!

 

[Chainsaw Jim]

I can't see that much advance causing that much of a problem unless it was maxed out to begin with. I'm assuming your spark plug is a non-resistor?

 

[spudulike]

I can't see that much advance causing that much of a problem unless it was maxed out to begin with. I'm assuming your spark plug is a non-resistor?

Yup, tried a number of plugs including an old mica one that must be 60-70 years that came with it.

 

[spudulike]

A bit of a follow up, had a dialogue with the company that supply me carb kits and it looks like there were no check valves in these early carbs and were only fitted in the later versions. The little brass plug merely covers the high speed nozzle and allows access to unblock it - looks like the issues may be elsewhere, guess I gotta work harder on this one!

 

[backhoelover]

have you tired raising the fulcrum lever any?

 

[spudulike]

have you tired raising the fulcrum lever any?

Yes, the manual specifies to lift it a little if a new seat is fitted.

 

[backhoelover]

have you pressure tested the carb

 

[spudulike]

Yes but I know the pop off was too high as I fitted a new spring so have refitted the old one with the aim of getting 8-12 psi pop off! hope to get on it again next week.

 

[spudulike]

Got the carb back together and eventually got the pop off back to around 12psi, checked the timing one last time and then with the H screw around 1/2 turn out and the L screw 1 1/2 turn out, it ran up and managed to get a tune on it. Got to put it through some wood but the chain was blunt.

Very loud, slow revving and unstoppable torque is my brief review. Looks like it is a runner at last.

Cheers to all

 

[heimannm]

You really have to love the old front tank McCulloch saws, nothing subtle about them.



Mark

 

[spudulike]

Yes, I just love their attention to making the saw as quiet as possible - I can see this from the ear defenders in the previous post.....