Wont start, running out of ideas

[picky]

Hi people,

1275 engine recently rebuild has been running fine until a week ago. I removed the distributor arm as I was parked in a bit of a rough spot, and when I put it back in later it was very difficult to start, it had no power at low revs at all, and needed lots of throttle to stop it from stalling. Once warmed up it appeared to be ok. After this happened, it would either start normally, or be very difficult to start, and again needed lots of throttle. I decided to investigate, distributor arm appears to be fitted correctly, I removed the spark plugs and cleaned them, they were very black (I have been doing alot of short trips recently and suspect it has not properly warmed up). Cleaned the plugs with a brass wire brush, and now it wont start at all. Power to the coil, regular sparks at the end of every lead when turning over. Fuel in the tank, fuel pump working, and fuel can be seen in and around the jet when the carb dashpot is taken off, so fuel is getting into the engine. Dashpot oil is topped up. After cleaning the plugs there is the occasional pop sound from the exhaust. Tomorrow I will check that there is compression on every cylinder, any other ideas? One weird thing is that the spark plugs were really hard to get out, had to put a bar on the end of the socket head to undo them. They were only put in recently.

[lambrettalad]

HI
Check your timing , by using the old method of a static light on your points,details in the books,when number one is before tdc,im not sure of the degrees? then change the plugs then try to start it .
you cant tell the timing by looking at the dizzy

[bmcecosse]

Wire brushing the plugs was a mistake - try another set - and do ease the threads so they run in nicely. Check the dizzy cap - is the little carbon brush present/correct? Try another rotor arm - amybe it was cracked when you removed/refitted it. And of course - are you sure the HT leads are on correct order 1342 anticlock round the dizzy?

[picky]

The plug leads were in the right order but all one position out! must have done this while trying a different dizzy cover. Its running a little rough at low revs, bmcecosse you reckon I have damaged the plugs by cleaning them with a wire brush? it was quite a soft one.

[Ratbag]

The plug leads were in the right order but all one position out! must have done this while trying a different dizzy cover. Its running a little rough at low revs, bmcecosse you reckon I have damaged the plugs by cleaning them with a wire brush? it was quite a soft one.

I'd vote for the impossible coincidence theory, and change the condensor.
There's a lot of it about lately.

Phil.

[Neil MG]

...also points condition and gap.

[picky]

Well the plugs taken out were really black and furry, so I think its been running very rich, and then a poor spark when cold. Its got electronic ignition now, so points etc is not relevant. I fitted a new set of plugs today and it cured the rough running, nice and smooth again. Going to check carb adjustment and take the plugs out after a run to see what they look like.

[bmcecosse]

Put a small tie-wrap round #1 plug lead at the cap - then you know what's what! And yes -wire brushing plugs scratches the ceramic and leads to HT shorts/poor running - throw them away!

[lambrettalad]

Hi yes ,often cleaning a plug doesn't do any good ,if you had a two stroke engine ,once a plugs gone its gone !!!!!

[picky]

Yes I think I will mark the dizzy cap for future reference! Interesting fuel issue: The car starts from cold without the choke. The tickover is too low when cold, and then rises once warmed up but is perfectly driveable from cold without any choke. But, when lifting the little piston push pin on the carb, the revs do not change at all (when warmed up) suggesting the mixture is ok. I will try the lift pin when cold just to see what happens. The spare set of plugs I fitted (which were cleaned with a brush, and did run rough as would be expected) Were very black and sooty even though only run briefly.

[beero]

Sounds like you need to adjust the screw on the choke cam. It raises the tickover when the choke is out.

[Neil MG]

If it starts and runs from cold without choke it is too rich.

How high are you lifting the piston with the pin?

You need to remove the air cleaner so you can see and you only lift no more than 1/16" (just over 1mm). If you lift all the way (much higher) you will not be able to judge the mixture based on idle change. Sometimes the pin sticks when it hits the piston and you are not lifting it at all (although the pin moves up to that point)

[picky]

I will check that the pin actually lifts the piston, I believe it does though, as when first setting up the engine the revs did change and I adjusted the mixture until it did not. Im lifting the pin until it stops! so maybe too much.

[bmcecosse]

It's way too rich -so weaken it off! The fuel consumption must be crippling.........