Rebuilt G80 wont start

[Spanielsam]

Hello again
Any advice as to where to start would be appreciated.
I have just rebuilt a 1956 G80S, engine, carburettor , etc
It did run before the rebuild all be it very roughly
I am now not getting any life out of the engine after the rebuild, despite very many kicks !
Is there an idiots guide as to what to check through?
I believe that I got the valve timing back correct and that the ignition timing is about right
I am getting a very big spark
The plug does not seem to be geting wet even after probably 20 kicks - is this normal ? I can tickle the carb and get petrol running out of the carb inlet
I am not even geting any splutter or back fire etc, how critical are the settings on these engines to even get some life out of them ?

I have never had a bike that is so difficult to kick over and it is making any random diagnostics very difficult for an arthritic old git like me 😄
Any pointers would be appreciated
Thanks in advance

[Les Howard]

I've suggested this a few times before but a quick check is to remove the spark plug but still have the HT lead on it a place it loosely near the plug hole but in a viewable position when kicking the engine over. Put your thumb tip to block the plug hole and kick over smarty. Your thumb should get blown off the hole with a pop at the very same time you witness the spark at the plug. If this happens things are roughly correct. You could pour in a teaspoon of petrol in the plug hole kick the engine over a few times and replace a good dry (or pre-heated) spark plug and attempt to start the bike by doing the "Just passed TDC" technique" not by kicking over like you would a twin cylinder engine from any crankshaft position which it seems you might be doing? The single cylinder "JPTDC" (my own acronym) method does not require massive leg force....Les

[SPRIDDLER]

I am now not getting any life out of the engine after the rebuild, despite very many kicks !
I believe that I got the valve timing back correct and that the ignition timing is about right
I am getting a very big spark The plug does not seem to be getting wet even after probably 20 kicks - is this normal ? I can tickle the carb and get petrol running out of the carb inlet

Hi Trevor
There may be some clues in another similar and long-running thread where in 8 pages we've just 'talked' through the basic checks to make:
http://www.jampot.com/forum/viewtopic.php?f=11&t=16023

I have never had a bike that is so difficult to kick over

Are you employing the correct procedure? i.e. bring up to compression, operate zorst lifter to bring just over TDC, release zorst lifter, long swinging kick....etc.
Follow the instructions in the Owner's Manual and it should be a doddle.

I believe that I got the valve timing back correct and that the ignition timing is about right

Do you have the Workshop Manual?
Do Les's 'thumb' test.
Are you sure you have timed the ignition with the A/R bobweights fixed at full advance and on the compression, not the zorst stroke?

......making any random diagnostics very difficult

How true!

Good luck.

[Spanielsam]

Thanks for the replies

Will definately do the "Les" test, i am pretty sure i set the points up on the compression stroke but need to check that again. I am trying to remember if the points cam rotates at engine speed or is it only 1/2 speed ? Can this be a revolution out ? Or does it use a wasted spark system ?


The exhaust lifter doesnt seem to make much difference when kicking the engine over and I have not been trying to start it as suggested , so the lifter needs checking as well and then give it a go

Just finished reading through the linked thread and a lot of good points made there although mine is standard points so should be easier to check

A fresh look at it is needed , i was geting frustrated yesterday 😡

Thanks again for your replies,mit really is good to know that I am not alone !

[iansoady]

The points (on a conventional system) run at half engine speed and it's very easy to set it up on the wrong stroke as I know to my cost....

But if the plug is showing no sign of petrol getting to it (a smell test is more sensitive than just looking to see if it's wet) then there's probably a carburation issue (as well?)

[Rob Harknett]

As has been said, you do need to set the ignition timing with the AR lever in the fully advanced position. You seem to talk as if you have not followed instructions on timing as set out in your bikes manual. This should had been the first thing you had had got before doing a thing to the bike. If the valve lifter does not work , even if the tappets are a long way out, you should be able to adjust the cable so it does work. Assuming that it's fitted correctly.

[bjork]

As well as most of the above advice it might be worth you visiting the local section. Whereabouts in Leics are you? You might be able to get someone to pop over and help. (or not help, possibly )

[ajscomboman]

As well as most of the above advice it might be worth you visiting the local section. Whereabouts in Leics are you? You might be able to get someone to pop over and help. (or not help, possibly )

Fishing for more beer Steve! I like your style although I don't know how you'll manage to fit it all in along with the trip to the states to sort out carb problems!

[Janet]

Fishing for more beer Steve! I like your style although I don't know how you'll manage to fit it all in along with the trip to the states to sort out carb problems!

Presumably he's still working so has the time. There's never enough time after you've retired.

[bjork]

Fishing for more beer Steve! I like your style although I don't know how you'll manage to fit it all in along with the trip to the states to sort out carb problems!

Presumably he's still working so has the time. There's never enough time after you've retired.

Well, sounds like you two have rumbled me? I do still work (a bit) but have more time to do my stuff now than I spend making someone else wealthy. So a quick trip over the pond to USA or wasn't it Canada? could be worked in to my own busy schedule.
My bag is packed ready so just waiting for the call now?
As soon as I remember when next club night occurs I will be available, in my usual surgery by the bar, for further consulting.

I'm all heart, me.