Cylinder Compression

David G · 09 April 2012, 10:15

Hi,
Is there any way of improving cylinder compression on one cylinder without stripping down and looking for worn rings, scored bore etc?

I have a 3 cylinder DT85 which according to my service agent is down about 10psi on the middle cylinder.

Cheers,

Orve.

Nos4r2 · 09 April 2012, 10:39

Quote:

Originally Posted by Orville

Hi,
Is there any way of improving cylinder compression on one cylinder without stripping down and looking for worn rings, scored bore etc?

I have a 3 cylinder DT85 which according to my service agent is down about 10psi on the middle cylinder.

Cheers,

Orve.

Improving? Only Redex-or QS powertune- if you've got a stuck ring. Otherwise, it's pull it apart.

The Slug · 09 April 2012, 11:48

I thought it was completely normal to see differences of up to 15psi? no doubt someone will correct me if i'm wrong. I owned a yamaha 115 that had a difference of about 10psi and it ran beautifully. i wouldn't worry about it and just keep using it as much as possible making sure not to run at low rpm for prolonged periods of time. In other words give it a good beasting every now and then which will help prevent build up of deposits/sticky rings

Nos4r2 · 09 April 2012, 12:06

Quote:

Originally Posted by The Slug

I thought it was completely normal to see differences of up to 15psi? no doubt someone will correct me if i'm wrong. I owned a yamaha 115 that had a difference of about 10psi and it ran beautifully. i wouldn't worry about it and just keep using it as much as possible making sure not to run at low rpm for prolonged periods of time. In other words give it a good beasting every now and then which will help prevent build up of deposits/sticky rings

10% not 10psi,though there's not much difference.

You're right though, a 10psi difference doesn't need pulling down, just monitoring. I should have said that in the original answer. Using Redex to free up a sticky ring would be a good idea though.

David G · 09 April 2012, 13:42

Quote:

Originally Posted by Nos4r2

10% not 10psi,though there's not much difference.

You're right though, a 10psi difference doesn't need pulling down, just monitoring. I should have said that in the original answer. Using Redex to free up a sticky ring would be a good idea though.

Thanks (and to The Slug too).

Does the Redex just go in the fuel or squirted more locally into the cylinder?

Chris · 09 April 2012, 13:58

The yanks rave about Sea Foam...

Seafoam Injector Cleaner & Engine System Carbon Cleaner | eBay

With the hours that they put on their engines they probably do have some experience with this.

Quicksilver Powertune is the same sort of thing.

Nos4r2 · 09 April 2012, 17:45

Quote:

Originally Posted by Orville

Thanks (and to The Slug too).

Does the Redex just go in the fuel or squirted more locally into the cylinder?

Redex and Seafoam are apparently pretty much the same thing from what I could gather on Iboats.com

You can try it either way.Be aware that redex through the fuel system can 'clean' the inside of the carbs nicely though and lodge any big bits of detritus it removes into the main jets.

Quicksilver Powertune might be better answer. Worth trying both.

Anchorhandler · 09 April 2012, 19:11

Hmmm, think the stuck ring is a bit of a long shot....

Do you know anyone with an endoscope/boroscope?...they're pretty cheap nowadays with some costing under the 100quid mark. If you know someone with one that will fit through the spark plug hole then take a look for any scoring etc... on the bores.

While your there, bung a bit of WD40 in the cylinder and let it sit overnight and see if it helps...just in case it is a ring stuck in its groove.

Simon