New Rebuild won't start

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Woody850

Woody850

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I have just put the rebuilt engine and gearbox back into the frame. All connections seem ok and there is 12.4 volts in the battery but no spark at the plugs.
I set the boyer at 31 degrees and have the Magnet in the upper hole of the stator while working with BTDC on the left cyclinder.
Power comes over the ignition, the oil lamp is on and blinkers work and of course both cleaned Premiers are feeding fuel.

I am completely stumped! Has anybody expierienced something like this?
 
Woody850 said:
I have just put the rebuilt engine and gearbox back into the frame. All connections seem ok and there is 12.4 volts in the battery but no spark at the plugs.
I set the boyer at 31 degrees and have the Magnet in the upper hole of the stator while working with BTDC on the left cyclinder.
Power comes over the ignition, the oil lamp is on and blinkers work and of course both cleaned Premiers are feeding fuel.

I am completely stumped! Has anybody expierienced something like this?
Click to expand...
12.4 volts is marginal. Is the battery new or in good condition? Even at 12.4 volts I would expect a spark at the plugs if laid against the cylinder head under no pressure so the most likely cause is a wiring problem. I'd also suggest setting the timing statically around 29 deg and fine tune it with a strobe light. This will avoid injury if you are off slightly and it kicks back.
 
No spark at plugs. Confirm coils have power at their terminals. Don't forget to assess the ign switch itself as these can have poor contact ot just the ign circuit. Try bypassing the switch as a test.

If good, check coil resistance across input terminals with all coonections removed. Check against coil Ohm specs. Do same check across an input terminal to the high tension socket and check against spec. Any open or zero reading tells you of a fault.

Next confirm a spark triggers if after connecting input terminals to +/- of battery, holding plug against cylinder head with a clamp etc, disconnect one power lead to a coil terminal. Should spark. If no, coil is bad.
If good, suspect something wrong with the Boyer, perhaps wiring or failure. Try a known good boyer/points/alternative EI.
 
Last edited:
I have boyer ignition, I was tidying wires and unplugged one to re-thread but didn't notice the pair of wires it was pushed into , after pluging in best guess , no spark ! Swapped that wire presto.
 
I gave the battery a charge up to 13,1 Volts and flooded the carbs again. The feeling of it wanting to fire it eventuelly did. Despite priming the oil lines it seemed like ages untill the return started feeding back to the oiltank.
This is the first run to warm the engine for the first torque but it began running very roughly if not on one cylinder.
I don't even know if I got the engine warm enough fot re-torqueing.
Has anybody expierienced sudden rough running.
 
Yes my 850 starting running rough, unable to increase road speed with more throttle. Turned out to be a carb intake manifold bolt coming undone and falling off while riding. Lots of air leaking into one side of engine, so effectively only one side of engine working.


Did you solve the no spark situation? How? Check for air leaks. Have you confirmed air restrictors (chokes; if fitted) are being fully lifted up from the handlebar control lever ? How are the carb idle jets? Float height/fuel level inside each float?
 
Tornado said:
Yes my 850 starting running rough, unable to increase road speed with more throttle. Turned out to be a carb intake manifold bolt coming undone and falling off while riding. Lots of air leaking into one side of engine, so effectively only one side of engine working.


Did you solve the no spark situation? How? Check for air leaks. Have you confirmed air restrictors (chokes; if fitted) are being fully lifted up from the handlebar control lever ? How are the carb idle jets? Float height/fuel level inside each float?
Click to expand...
Yes it must have been partly low battery and not enough fuel but everything is set up fine, could be an air leak, must check though. I had that problem long long ago on a T140v where I forgot to blank of the mounting point for the choke handle.
 
triumph2 said:
12.4 volts is marginal. Is the battery new or in good condition? Even at 12.4 volts I would expect a spark at the plugs if laid against the cylinder head under no pressure so the most likely cause is a wiring problem. I'd also suggest setting the timing statically around 29 deg and fine tune it with a strobe light. This will avoid injury if you are off slightly and it kicks back.
Click to expand...
Hi Woody (and all),
At the risk of politely disagreeing with you I would think that any ignition system that failed to deliver a spark sufficient to start an engine with 12.4 volts as totally useless and incapable. I suspect that most any ignition system could drop towards 8 volts and still manage to get a start.
just a thought, probably wrong
alan
 
Alan L said:
Hi Woody (and all),
At the risk of politely disagreeing with you I would think that any ignition system that failed to deliver a spark sufficient to start an engine with 12.4 volts as totally useless and incapable. I suspect that most any ignition system could drop towards 8 volts and still manage to get a start.
just a thought, probably wrong
alan
Click to expand...
Hello Allan,
that was the reason why I went ahead to try it with 12.4 volts. Thinking more it just didn't get enough fuel but I am annoyed that I didn't get the engine really warm for the first torque. What do you think:
1. Torque and run untill it is warm and torque again
or
2. Warm the engine again untill then do the first torque?
 
Woody850 said:
Hello Allan,
that was the reason why I went ahead to try it with 12.4 volts. Thinking more it just didn't get enough fuel but I am annoyed that I didn't get the engine really warm for the first torque. What do you think:
1. Torque and run untill it is warm and torque again
or
2. Warm the engine again untill then do the first torque?
Click to expand...
Warm the engine again.

New engines can burn oil, oil trapped in honing marks, applied to valves and guides, etc.

You sure you‘ve not simply oiled a plug ?
 
Yes - could be oil-fouled. Interesting how cylinder/piston oiling procedures have changed over the years. Opinions/methods have gone from dipping the piston (attached to the rod) in 30 wt engine oil and installing it to installing it dry and various levels of lubrication between those extremes. Obviously, depending on the method, different amounts of oil could end up on the plugs.
 
MexicoMike said:
Yes - could be oil-fouled. Interesting how cylinder/piston oiling procedures have changed over the years. Opinions/methods have gone from dipping the piston (attached to the rod) in 30 wt engine oil and installing it to installing it dry and various levels of lubrication between those extremes. Obviously, depending on the method, different amounts of oil could end up on the plugs.
Click to expand...
Yes I go with you there, after it cooled I pulled the plug on the right cyclinder and Black it was. I put in another when cold and tried it again but it pops and gives the occasional splatt once backfiring on the right cyclinder.
All has been checked regarding an air leak but that seems good.
 
I have dealt with similar symptoms on a MK 3 built by an unnamed shop north of MA and West of NH. I could clearly see that the pipes were blued to second bend, but the customer was able to start it; it had a real lumpy idle and no power until it got past 5000 RPM. After correctly adjusting the back-fire clutch, and checking the static timing with no difference I put a degree wheel on and discovered that the cam was way out of time by 5 rollers. Also what was clear is that the monkeys who built the motorcycle never test rode it and couldn't get it started when the customer came to pick it up!!!

When it was brought to me it was on it's second owner.

I suggest that you check the cam timing if, after every other possibility has been explored including a compression check by leak down or by max psi.

Best.
 
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