Low compression after rebuild, won't start

[Duncan]

If you have a new Monobloc did you strip and clean before fitting it? Occasionally there can be some foreign material in it.

[simonh]

This morning's update. Still nothing. I have re-checked everything, charged battery, put petrol down the plug hole, tried easy start, not a cough. Timing checked countless times, 1\4 " BTDC. White dot showing through the hole before the pickup coil rotor anti clockwise. I have a brand new monobloc, bought from RGM Norton jetted to the book settings. Pilot air 1.5 turns out. I can hear the engine sucking when I kick over. Compression seems ok in that the clutch slips a bit , which it didn't do with the other barrel. Plug doesn't seem wet, but not sure what I need to check in the carb if anything.

[Mick D]

Hi

I'm surprised you haven't at least had a splutter - try putting a little fuel, (1/2 teaspoon), into the carb inlet and see if the engine fires, if not I'd be looking at an ignition fault.

If it fires you need to inspect the carb, easiest place to start and most likely to be at fault is the pilot jet, remove it and ensure it is clear.

Does the carb 'tickle'?

Regards Mick

[Andy G]

Can anyone in Cheshire give Simon a visit? Seems like he's checked everything logical but a second set of eyes often helps in my experience!
The only other suggestion I have is to get some willing enthusiasts to try to bump start it?

[Andy G]

Oh, and sounds obvious but fuel tap open and float chamber filling? As Mick asks...does carb tickle?

[SPRIDDLER]

I'm intrigued and I understand that you haven't had it running at all.

With all the kicking over the plug should be getting wet. Even though it's a new carb I'd check as Mick and as Druncan suggested that the pilot jet and its drillings aren't blocked. And you should be able to get petrol dripping from the carb if you hold down the tickler.

Electronic ignition is an unknown to me and although I'm aware of 'wasted spark' systems I note you said that you 'think' your Boyer sparks at every revolution. If you have a spark and compression you should get some sort of reaction especially when using highly volatile Easy Start. I suspect the ignition timing is out so I had a look on the Boyer website to find out more. I didn't find much as I don't know which unit you have but I did see this, the first bit of it may be relevant:...........


I Have Sparks On Cranking But It Won't Fire
Check the stator wires do not change colour in the wiring loom, as swapping these will make the ignition fire over 50 degrees retarded. With a digital system check you have suppressed plug caps fitted of approx. 5000 ohms. If timing has just been done, don't forget that the timing angle on the camshaft is half of the crankshafts (i.e. on a 650 triumph full advance timing is 38 degrees crankshaft but is set at 19 degrees on the camshaft).

Oh, and your Profile still shows you as a 'Guest' so you may wish to let the webmaster@jampot.com know so that you can access all the club site.

[simonh]

Good afternoon all. I think I am at the stage where physical help would be appreciated. I stripped and reassembled the carb, blew out all drillings with airline. I admit that it sounds like ignition, but I have re-checked the firing point so many times, I have lost count. I've restored quite a few bikes and have been working on them for decades, but this one has me beat at present. I even tried known good petrol and spark plug from my model 31 which was ridden today. I am using the Boyer ignition, set up as per one of the club members, on Fix yet website. I decided to go with Boyer as I was unsure of my Wipac points and condenser + no availability when I looked.I am using an auxiliary fuel tank. So no tap or blocked filter etc. I am away on business for a couple of days from tomorrow, so will get my breath back and have another go midweek. Thanks again for all support

[simonh]

Also, the Boyer ignition has a 2 wire loom to the stator plate and the colour is correct Both ends. 125psi + compression now. I will probably disconnect the Boyer and try the old points setup next weekend.

[ajscomboman]

So what was the issue with the compression? 50 to over 125 PSI

[clanger9]

Does the piston come all the way to the top of the barrel at TDC? I'm wondering if it's somehow got a 250 crank...