Lack of power

[JohnD]

Roger,

Your compression numbers are  "okay (ish) ".  The actual number is irrelevant - the gauges are not precision instruments!     They are excellent to compare pressure across the block, but cannot be used to compare with readings from someone else, unless they are done on the same day with the same gauge.      If your readings are +/- 5% across the block, then fine!     

And, oil on the bore always increases the pressure - even well-sealing rings have their seal improved by some oil in the lands!    The Oil Test tells you if a low pressure is due to poor valve sealing, when the oil doesn't improve pressure.

IMHO, you are quite correct to pursue a different  cause for low power.   You found and sorted a carburettor problem, well done.  Ensure that ignition timing correct and use Equal Lift on Overlap  (only the rocker cover needs to come off!) as a check that cam timing correct.

John

[johny]

Going back the carb pistons, can you lift them with your finger all the way up (engine not running) and then they drop back down with a nice clunk as they hit the bridge?

[Roger]

13 minutes ago, JohnD said:

the gauges are not precision instruments!

Thanks John, no they are certainly not calibrated, at least not the one made in China that I use. However, the company I work for actually make pressure gauges that ARE precision instruments 🙂 They are used in the semi conductor industry, and are "Made with Pride on The Åland Island" 🙂 https://www.inficon.com/en/products/vacuum-gauge-and-controller/cube-cdgsci

I will re-check timing, I only adjusted it to 13 degrees static and have not used a timing light yet.

[johny]

While checking timing with strobe see if it advances when you rev the engine and that the dizzy centrifugal weights are not seized (see manual for the amount of advance you should be getting).... 

[JohnD]

Roger, if you were using your company's product then of course my previous comments don't apply!   However, then what do you compare your readings with - everyone else is using non-precision kit, so their readings are doubtful, if yours are not! 

Can anyone say what compression should be, if the instrument is calibrated and precise?  I fear it depends on the state of tune of the engine, but a figure for a standard rebuilt engine would be of interest.   

John

 

 

[Pete Lewis]

and dont discount the 6 cyl damper ring may have lost its adhesion and the tdc timing marks on the damper ring are wildly out of place 

Pete

[Roger]

1 hour ago, johny said:

can you lift them with your finger all the way up (engine not running) and then they drop back down with a nice clunk as they hit the bridge?

Yes, very nice clonk! 🙂

[Roger]

5 minutes ago, Pete Lewis said:

dont discount the 6 cyl damper ring may have lost its adhesion and the tdc timing marks on the damper ring are wildly out of place

I did check this using one of those tiny cameras you can push into the cylinder throught the spark plug hole. Marks where they should be! ✅

[Pete Lewis]

if the diaphragms are fitted with thelugs located looking down with the top cover off the two holes in the air piston base must be towards the engine.

easy to check just 2 x 4 screws 

and do turn the dizzy by hand to find the bests running and then retard it a little from best 

ignore the marks they may be wrong 

Pete

[Roger]

Lugs and holes are where they should be, I checked that when I replaced the diaphragms. Timing is definitely next on the list!

[Pete Lewis]

running out of ideas sorry if im repeating the obvious 

but a 25 horse smile is getting there 

pete

[Roger]

4 minutes ago, Pete Lewis said:

running out of ideas sorry if im repeating the obvious

I need all the help can get! I appreciate all advices and I check them all. Keep them coming...

[Pete Lewis]

maybe give the main  fuel line a blow out , 

Pete

[JohnD]

3 hours ago, Pete Lewis said:

and dont discount the 6 cyl damper ring may have lost its adhesion and the tdc timing marks on the damper ring are wildly out of place 

Pete

Thanks, Pete, the old Hobby Horse needs a ride now and then!

[Roger]

I had to take a break from my project due to travelling for work. The plan is to find those missing horses this weekend. Air leaks and/or fuel starvation is what I suspect. I think I set the fuel level in the carbs a bit too low in my efforts to make the carbs stop flooding. I took them apart (again....) and the float height seems to be closer to 20 mm instead of the specified 18 mm. Bigger height = lower fuel level I guess. Don't know if that deviation is enough to create the problems I have (?). Anyway, will re-adjust and make sure I get as close as possible to 18 mm.

Back to airleaks. The carb spacers I have do not look good. I don't want to grind them in any way since I don't know if they contain asbesthos. I have tried to order new ones, but the ususal suspects don't seem to have them in stock. Do anyone on here know if spacers for CD 150 are available? If so, where can I buy them?

 

[dougbgt6]

These guys do this one which is for my CD150s, but it has the cut out. There are variants on the site they may have the right one?

Spacer block - SC Parts Group Ltd

Doug

[Roger]

15 minutes ago, dougbgt6 said:

There are variants on the site they may have the right one?

Thanks Doug, I will check what they have.

[Roger]

I did some research and it seems like the SU HS4 has the same diameter 1,5". Anyone know if this HS4 spacer would fit my CD150´s?

https://sucarb.co.uk/insulating-manifold-air-inlet-gaskets/insulating-gaskets/insulating-gasket-5.html

[Iain T]

Roger, I bought my correct isolator without the cutout from Chic Doig. 

As to the SU isolator all I can say is I bought stub stacks made for an SU but had to elongate the fixing holes to fit my CD150 Strombergs. 

Iain 

Edited September 30, 2023 by Iain T

[daverclasper]

I bought a couple of NOS spacers off Mick Dolphin (nice guy) maybe about 18 months ago