308 won't fire

[Sandaro]

Hi all,

Just put a new 308 in my hq premier and can't get it to fire. To try to find fault I have put coil, dissy, starter in from my other working 308, but still no go. I have the dissy round the right way with timing set basically at top dead centre at cranking speed (and have moved it to either side while cranking but still no go)

ATM it cranks on starter, there is spark at the spark plugs, put fuel down the guts of the carby, but still no fire (or misfire). Its like the kill switch is on, but it doesn't have one.

I have read previous answers to a post where someone had a similar problem, and note that HK said replace the ignition switch, and Tally said to check ignition switch by running a bypass wire direct from starter to coil.

My questions on this advice- is it applicable if I've got spark at the spark plugs? And in doing the bypass check wire from starter to coil, is that left on once if the motor starts, or removed immediately once engine fires?

Thanks in advance for any help, Steve

[XX7SANDMN]

i would leave bypass wire on but sounds like 180 degrees out check tdc with rh rocker cover off both number 1 valves should be closed and rockers at top and level good luck

[HZSM50]

Hi Steve,

By passing the ignition switch is the best way to check if there is a problem with the switch, and other problems too.
If it starts with the by pass you don't have to take it off if you want to tune it up before you check for the problem your having, you can however turn the ignition off and
the engine should keep running.
You can take power from the battery as well as the starter, But if you have spark then it is unlikely to be the ignition.
Double check all your timing marks to make sure they are correct. Also check for cracks in the dissy cap and make sure there is no earthing of the spark.
This happened to me a long ago it drove me nuts.

[HK1837]

Dont run it for too long with a bypass wire if it is a 9V coil or you'll cook the coil.

Sounds like a dud coil or suppressor in the dizzy, or a poor connection in the LV side of the coil IF the dizzy is installed correctly.

[Sandaro]

Thanks for the feedback, I had already checked the dissy position (ie not 180 degrees out) using the rocker location as suggested. Will try the bypass wire tonight and report back.

[HK1837]

Being a HQ the plug in the firewall might have corrosion in it. Try unplugging it and cleaning all the contacts.

[Sandaro]

Have determined that all electrics are fine, have discovered low/no compression, seems bloody dodgy amateur engine builder (me) assumed standard pushrods would be fine and didn't check length.

Looks like a new set of pushrods or shims under rockers? not sure if this is done, or whether guide plates are used to achieve this

[HK1837]

Is it a reground cam? If so you'll need adjustable rockers or get the rocker pivots machined down to the correct level as given by the cam manufacturer.

Or are you saying the cam base circle is too big so it is holding rockers/valves open? If that is the case the rocker bridges may already have been machined for a reground cam, so you need new ones.

[Sandaro]

Yeah 2nd option, the valves are being held open, its a new cam, not reground.

[HK1837]

I'd compare the bridges to a new one. Then check the cam's base circle.