25 replies to this topic

[paul1380]

Hi guys 

 

I have just finished rebuilding my 1380 engine just gone to start it and it wont fire up wont's to but nothing.

I have just run a compression test and NO:4 cylinder is only pushing 3 psi.

New piston rings were fitted and all off set to each other not sure but could it be the rings are not sealing correctly was wondering if a drop of oil in the cylinder would do the trick? then turn it over to see if it makes a better seal or opens the ring up if it is stuck?

Any help would be great full as i don't wont to strip it down again.

[ChopperHarris]

blimey...you should get more than 3psi with no rings!

Valve stuck open?

[ChopperHarris]

Oil down the plug hole and try again, if it improves then its piston/ring/bore related

[carbon]

blimey...you should get more than 3psi with no rings!

Valve stuck open?

 

You can get 120psi compression with top rings all broken into small pieces.

 

Agree with ChopperHarris, check the valves are closing fully.

[GraemeC]

I'd definitely suspect valve train, compression that low isn't Pistons or head gasket (unless the piston are well under sized!)

Edited by GraemeC, 12 February 2016 - 05:57 PM.

[Cooperman]

The only way the compression can be that low is:

 

A valve stuck open.

A valve not correctly adjusted

A piston with a hole in it

A hole or split in the wall of the bore and no coolant in the block.

A broken compression tester

[paul1380]

Ok thanks guy's i have put oil down the bore and compression has come back i am going to recheck the valve adjustment they are set at 16".

No holes in the piston have checked for coolant in the oil nothing thank god :) got it to fire and tick over but died so thinking it is a fueling problem.

Running it on a DCOE 40 Weber need to check the float level and make sure the pump is pumping enough fuel.

 

Thank's for  all the good advice guy's i will let you know the out come.

[gazza82]

16" ????

Guess you meant 16 thou ...

[Fast Ivan]

Running it on a DCOE 40 Weber need to check the float level and make sure the pump is pumping enough fuel.
 
Thank's for  all the good advice guy's i will let you know the out come.

Make sure you don't over fuel it though

[Spider]

Were all the valve stems coming up close to the same height as each other when the Valves are closed?  I ask, because it could also be a bent valve. Sorry, I can't see how a fuelling issue might be behind such a low compression pressure reading.

[paul1380]

Hello again

 

yes gazz82 i did mean 16 thou.

                                                                                                                                                                                                                                                                                Just been out and recheck the compression all good looks like i had a ring that had got stuck :) 

going to readjust the tappets tomorrow just to make sure. The problem i am having now is the DCOE 40 Weber will only start the engine and run by using the choke and will not work on the throttle as soon as it throttles it just does nothing so i might just run it on a HIFF carb in stead.

[WimpyMiniMan]

Hello again

 

yes gazz82 i did mean 16 thou.

                                                                                                                                                                                                                                                                                Just been out and recheck the compression all good looks like i had a ring that had got stuck :) 

going to readjust the tappets tomorrow just to make sure. The problem i am having now is the DCOE 40 Weber will only start the engine and run by using the choke and will not work on the throttle as soon as it throttles it just does nothing so i might just run it on a HIFF carb in stead.

Sounds like your running your Weber way too lean - there should be a small screw somewhere on the carb to adjust fuel mixture. If you think about it, if it only works with the choke then your mixture must be too lean as it should start and run smoothly when warm without the choke being operated. I would get it up to operating temperature, turn your engine off, and then adjust the fuel mixture screw (richen) until it will start without the choke. You may also find you need to adjust your idle speed aswell.

Edited by WimpyMiniMan, 16 February 2016 - 07:52 PM.

[paul1380]

All done getting 130 psi from all cylinders as i have put RILSONE compression repair into the iol and it has done the trick looks like it was a sticky ring thanks for all your help :) 

[MRA]

16" ????

Guess you meant 16 thou ...

 

Yep 16 inches would save wear on your valvetrain,

 

16" = 16 inches

0.016" = 16 thousandths of an inch or 16 thou.

[Carlos W]

You need to run it lean when you're running it in.