Updated 28th July.

If you are unable to login, you probably need to read this change to your username & profile.

 

Welcome, Guest
Username: Password: Remember me

TOPIC:

Bedford K Model Cylinder Compression 06 Mar 2020 22:19 #207222

  • hayseed
  • hayseed's Avatar
  • Offline
  • Posts: 4232
  • Thank you received: 703
I'm with Lang, you have badly worn/Burnt Valves... IMHO
"Be who you are and say what you feel...
Because those that matter...
don't mind...
And those that mind....
don't matter." -

Please Log in to join the conversation.

Bedford K Model Cylinder Compression 06 Mar 2020 22:44 #207225

  • cobbadog
  • cobbadog's Avatar
  • Offline
  • Posts: 2261
  • Thank you received: 975
Yes this is what I meant, the valves are or may not be seating and a valve grind at least would be a big help. As Lang suggested maybe the valves have eroded away and is why your compression is down.
I recently bought a new compression gauge kit and it advised what has been mentioned, warm the engine, pull the plugs out, throttle and choke wide open, and crank over the engine for at least 6 compressions per cylinder being tested. Once you have a reading let it stand for 30 seconds to see if it drops or not. If it drops it is time to have a look inside and start at the valves and if they are ok then you go deeper to rings. I saw a small single cylinder 2 stroke engine loose compression and low and behold the rings had moved around to be in alignment and compression was getting passed the ring gap. This happened because the brass peg fell out. Made a new peg and put the lot back together and it still runs like a clock.
Cheers Cobba & Cobbarette
Coopernook, The Centre of our Universe.
STUBBOURN B@ST@RD

Please Log in to join the conversation.

Bedford K Model Cylinder Compression 07 Mar 2020 09:07 #207231

  • Pierre
  • Pierre's Avatar Topic Author
  • Offline
  • Posts: 495
  • Thank you received: 219
Thanks guys, I'll work along those lines.
I need to pull the engine & gearbox as the welch plug has gone at the back of the motor (inside the bell housing).
So quite a bit of work ahead.
I retired last week, so should be able to get a move on this year.
Will put some photos up after the long weekend,
cheers
Pierre
Pierre

Please Log in to join the conversation.

Bedford K Model Cylinder Compression 07 Mar 2020 09:26 #207234

  • Morris
  • Morris's Avatar
  • Offline
  • Posts: 1799
  • Thank you received: 572
Pierre,
As you have found, it always seems to be the most difficult welch plug that leaks. I NEVER replace one welch plug. I do them all at the same time so I will not have to do one again.
I have my shoulder to the wheel,
my nose to the grindstone,
I've put my best foot forward,
I've put my back into it,
I'm gritting my teeth,

Now I find I can't do any work in this position!

Please Log in to join the conversation.

Bedford K Model Cylinder Compression 07 Mar 2020 09:57 #207236

  • Sarge :-X
  • Sarge  :-X's Avatar
  • Offline
  • Posts: 2642
  • Thank you received: 302
Pierre, my O had the same Welch plug issue, at the back of the motor, it's just above the bell housing, you can either cut a hole in the fire wall or as I was advised by more experienced practitioners here, knock the old plug inwards then fit a new one on top. Second method was the choice. And like Morris said, I had to do all the others first. A lovely old truck with a nice purr as long as 38 mph is your speed.
Sarge B)
ACCO Owner, Atkinson dreamer.

Please Log in to join the conversation.

Bedford K Model Cylinder Compression 07 Mar 2020 15:50 #207246

  • jon_d
  • jon_d's Avatar
  • Offline
  • Posts: 423
  • Thank you received: 116
Agree; with those figures, it looks like the major leakage is in the valves.

Unless -of course, if the rings and bores are so worn or broken that the oil is leaking past the pistons.

If its not smokey, and doesn't blow smoke at the bottom of a hill; it may just require a valve grind.

Please Log in to join the conversation.

Last edit: by jon_d.

Bedford K Model Cylinder Compression 07 Mar 2020 21:43 #207253

  • cobbadog
  • cobbadog's Avatar
  • Offline
  • Posts: 2261
  • Thank you received: 975
When I have replaced welsh plugs in the past I always used the plain steel ones in all the easy to get to places and brass in the bastard places. I know they are designed to rust away instead of the block but I never felt like having to pull the engine out again for the awkward ones and then I run inhibertor as well with anti-freeze.
Cheers Cobba & Cobbarette
Coopernook, The Centre of our Universe.
STUBBOURN B@ST@RD

Please Log in to join the conversation.

Bedford K Model Cylinder Compression 07 Mar 2020 22:59 #207260

  • JOHN.K.
  • JOHN.K.'s Avatar
  • Offline
  • Posts: 2372
  • Thank you received: 752
No one ever used rust inhibitor,unless you had a Cummins,I ran a Perk on a topup evry morning with tapwater.......but do that with a modern motor,lucky if it lasts 6 months.Caterpillar motors use stainless steel plugs ,never seen one evn tarnished by the water.

Please Log in to join the conversation.

Bedford K Model Cylinder Compression 07 Mar 2020 23:50 #207263

  • overnite
  • overnite's Avatar
  • Offline
  • Posts: 1331
  • Thank you received: 393

Yes this is what I meant, the valves are or may not be seating and a valve grind at least would be a big help. As Lang suggested maybe the valves have eroded away and is why your compression is down.
I recently bought a new compression gauge kit and it advised what has been mentioned, warm the engine, pull the plugs out, throttle and choke wide open, and crank over the engine for at least 6 compressions per cylinder being tested. Once you have a reading let it stand for 30 seconds to see if it drops or not. If it drops it is time to have a look inside and start at the valves and if they are ok then you go deeper to rings. I saw a small single cylinder 2 stroke engine loose compression and low and behold the rings had moved around to be in alignment and compression was getting passed the ring gap. This happened because the brass peg fell out. Made a new peg and put the lot back together and it still runs like a clock.


Cobbadog, I thought you were going to say you gave the 2 stroke a valve grind, and then you had good compression.
The following user(s) said Thank You: cobbadog

Please Log in to join the conversation.

Bedford K Model Cylinder Compression 08 Mar 2020 10:21 #207268

  • PDU
  • PDU's Avatar
  • Offline
  • Posts: 1193
  • Thank you received: 750
Look on the bright side Pierre at least it is better than finding the broken valve spring that was hiding under the rocker cover.

I knew my engine was locked, and I knew the valve spring was broken, but it's nice to know how bad things are, so quiet Sunday morning tear down.
The way I figure it, the valve spring broke, consequently the cam follower wasn’t pushed down, the valve and piston started butting heads until the valve stem snapped, and then the piston started to disintegrate, eventually leaving the connecting rod with the remaining chunks of piston to beat the crap out of the cylinder wall!

Ho, hum, time to find another engine . . . :S

Please Log in to join the conversation.

Last edit: by PDU.
Time to create page: 0.483 seconds

Historic Commercial Vehicles Club of Australia Inc.  Post: P.O. Box 2020 Bayswater Vic. 3153    Clubrooms: Unit 8 / 4  Macquarie Place Boronia    Club Phone: 0400 025 525    Club Rooms:  03) 9738 1558