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New build - need help with CV40 carb set up please

Started by Adam76, October 27, 2021, 11:03:29 PM

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0 Members and 2 Guests are viewing this topic.

Hossamania

Usually the rear cylinder runs leaner than the front. A compression and leak down test will rule out ring or valve issues, or even the cam chain being off by one tooth. Once that is done, proper spark needs to be established. Since the fuel shares a common manifold and carb, there should not be a big difference in afr, provided your intake seals are good. That leaves spark or cylinder seal being the issue.
Hopefully I'm on track, maybe someone else can chime in and redirect if I'm off base.
Double check your plug wires, make sure tight connection at the coil, no rubbing anywhere, maybe even put the old ones back on for a test ride.
If the government gives you everything you want,
it can take away everything you have.

Don D

Put a new set of plugs in it and ride it a while, say another 50 miles then post the plugs photos ground straps visible. It is time to change the oil.
As Hoss said, compression test is wise.

rigidthumper

Quote from: Hossamania on November 02, 2021, 05:28:00 AM
Usually the rear cylinder runs leaner than the front. A compression and leak down test will rule out ring or valve issues, or even the cam chain being off by one tooth. Once that is done, proper spark needs to be established. Since the fuel shares a common manifold and carb, there should not be a big difference in afr, provided your intake seals are good. That leaves spark or cylinder seal being the issue.
Hopefully I'm on track, maybe someone else can chime in and redirect if I'm off base.
Double check your plug wires, make sure tight connection at the coil, no rubbing anywhere, maybe even put the old ones back on for a test ride.
As I look at those plugs, my initial thought is a tiny bit of oil is passing the rings/seals, and there's an intake seal passing a little extra air. I'd pull/inspect/reinstall the intake seals (all 3), adjust the accelerator pump nozzle to squirt directly on the needle, new plugs and try again.
Ignorance is bliss, and accuracy expensive. How much of either can you afford?

speedzter

November 02, 2021, 05:52:25 AM #53 Last Edit: November 02, 2021, 05:57:06 AM by speedzter
Compression can show up cam timing issues.
What exhaust and air cleaner are you running.
A carb'ed HD will nearly always have the front and rear cylinders running a different mixture, but not as extreme as your plugs indicate.
I would also swap out the needle for a stock one.

Adam76

Quote from: Hossamania on November 02, 2021, 05:28:00 AM
Usually the rear cylinder runs leaner than the front. A compression and leak down test will rule out ring or valve issues, or even the cam chain being off by one tooth. Once that is done, proper spark needs to be established. Since the fuel shares a common manifold and carb, there should not be a big difference in afr, provided your intake seals are good. That leaves spark or cylinder seal being the issue.
Hopefully I'm on track, maybe someone else can chime in and redirect if I'm off base.
Double check your plug wires, make sure tight connection at the coil, no rubbing anywhere, maybe even put the old ones back on for a test ride.

I'm trying to find someone who will do a compression test / leakdown.... the Harley workshops are booked out for 6 weeks and non Harley mechanics don't want to even do just a simple compression test....

I'm testing the intake seals with a spray bottle of soapy water.

Thanks to all the folks still responding to my thread. I hope I get it sorted. Cheers

Adam76

Quote from: HD Street Performance on November 02, 2021, 05:39:35 AM
Put a new set of plugs in it and ride it a while, say another 50 miles then post the plugs photos ground straps visible. It is time to change the oil.
As Hoss said, compression test is wise.

Ok thanks. I'm onto my third set of NGK plugs and I've just changed the oil.
I'm going to check the intake manifold for leaks next.
Then maybe another 50 mile road test?
Cheers

Adam76

November 03, 2021, 02:01:51 AM #56 Last Edit: November 03, 2021, 03:05:46 AM by Adam76
Quote from: rigidthumper on November 02, 2021, 05:41:19 AM
Quote from: Hossamania on November 02, 2021, 05:28:00 AM
Usually the rear cylinder runs leaner than the front. A compression and leak down test will rule out ring or valve issues, or even the cam chain being off by one tooth. Once that is done, proper spark needs to be established. Since the fuel shares a common manifold and carb, there should not be a big difference in afr, provided your intake seals are good. That leaves spark or cylinder seal being the issue.
Hopefully I'm on track, maybe someone else can chime in and redirect if I'm off base.
Double check your plug wires, make sure tight connection at the coil, no rubbing anywhere, maybe even put the old ones back on for a test ride.
As I look at those plugs, my initial thought is a tiny bit of oil is passing the rings/seals, and there's an intake seal passing a little extra air. I'd pull/inspect/reinstall the intake seals (all 3), adjust the accelerator pump nozzle to squirt directly on the needle, new plugs and try again.

Ok thanks. I have the air cleaner off  - how do I adjust the accelerator pump nozzle? It's shooting way off  the needle
Cheers

Adam76

Quote from: speedzter on November 02, 2021, 05:52:25 AM
Compression can show up cam timing issues.
What exhaust and air cleaner are you running.
A carb'ed HD will nearly always have the front and rear cylinders running a different mixture, but not as extreme as your plugs indicate.
I would also swap out the needle for a stock one.

Hey speedzter, how's it going. A/C is std Ness big sucker. Pipes are factory headers and old style SE mufflers (the non restrictive ones).

Yes, 100% there's always going to be a small difference in afr between the front and rear, but this difference is large and also it's usually the front cylinder that runs slightly rich and the rear a tad leaner. AFAIK.

The needle is a genuine CV Performance needle  - do you think that is the problem?

Cheers

Adam76

November 03, 2021, 02:19:20 AM #58 Last Edit: November 03, 2021, 02:34:14 AM by Adam76
I also had the valve guides replaced  when the machine shop did my cylinder boring etc... Do you think it could be a bad valve guide seal?

If the plug was black and oily, then you would suspect bad rings seal? Is that right?

Hossamania

November 03, 2021, 04:12:32 AM #59 Last Edit: November 03, 2021, 04:19:05 AM by Hossamania
Just guessing on rings and valves without a compression and leak down test.
Rather than soapy water spray, use carb cleaner and listen for the idle to change if the spray gets sucked in. Leaves no mess like soap does. Some use propane instead of spray.
You may be able to find a compression tester for not a lot of money.
As far as the spray jet, if I remember right, it just twists with a pliers, but wrap the jaws to protect the brass, and do not do this until someone else chimes in here to confirm that.
The needle could be an issue, put the stock one back in for a test. Is the CVP needle adjustable? If so, which groove is the clip set at?
If the government gives you everything you want,
it can take away everything you have.

Adam76

Quote from: Hossamania on November 03, 2021, 04:12:32 AM
Just guessing on rings and valves without a compression and leak down test.
Rather than soapy water spray, use carb cleaner and listen for the idle to change if the spray gets sucked in. Leaves no mess like soap does. Some use propane instead of spray.
You may be able to find a compression tester for not a lot of money.

Thank you  👍

Should my accelerator pump nozzle be squirting toward the needle? Mine goes way in front of the needle.

Hossamania

I modified my response to answer some of those questions.
Yes, you want the jet to spray straight into the throat.
If the government gives you everything you want,
it can take away everything you have.

rigidthumper

I use a small pair of duck bill pliers with a good cross hatch on them. Helps to grab without damaging/crushing the nozzle. I adjust so the spray hits the needle jet/jet needle. I believe this helps break up the fuel and starts the atomizing process before it passes the valves. Hitting the needle also prevents direct spray on just 1 cylinder.
Then again, I eat crayons ;)
Ignorance is bliss, and accuracy expensive. How much of either can you afford?

Adam76

Quote from: Hossamania on November 03, 2021, 04:12:32 AM
Just guessing on rings and valves without a compression and leak down test.
Rather than soapy water spray, use carb cleaner and listen for the idle to change if the spray gets sucked in. Leaves no mess like soap does. Some use propane instead of spray.
You may be able to find a compression tester for not a lot of money.
As far as the spray jet, if I remember right, it just twists with a pliers, but wrap the jaws to protect the brass, and do not do this until someone else chimes in here to confirm that.
The needle could be an issue, put the stock one back in for a test. Is the CVP needle adjustable? If so, which groove is the clip set at?

Thanks 👍

I've got carb cleaner to test for intake leaks.
I'm picking up a compression tester today to check both cylinders.
I'm adjusting the pump nozzle to spray directly at the needle.
I'm swapping the non adjustable CVP  needle out to put the stock needle back in.
Then I'm going for another test ride.

Thanks for all the help and suggestions. I'll report back with my findings.
Cheers. 

Adam76

Quote from: rigidthumper on November 03, 2021, 09:19:02 AM
I use a small pair of duck bill pliers with a good cross hatch on them. Helps to grab without damaging/crushing the nozzle. I adjust so the spray hits the needle jet/jet needle. I believe this helps break up the fuel and starts the atomizing process before it passes the valves. Hitting the needle also prevents direct spray on just 1 cylinder.
Then again, I eat crayons ;)

How do those crayons taste? 🤪

Thanks for the details, I'll get to it later today.
Cheers

Hossamania

Quote from: Adam76 on November 03, 2021, 04:38:00 PM
Quote from: rigidthumper on November 03, 2021, 09:19:02 AM
I use a small pair of duck bill pliers with a good cross hatch on them. Helps to grab without damaging/crushing the nozzle. I adjust so the spray hits the needle jet/jet needle. I believe this helps break up the fuel and starts the atomizing process before it passes the valves. Hitting the needle also prevents direct spray on just 1 cylinder.
Then again, I eat crayons ;)

How do those crayons taste? 🤪


They make for colorful poops!
If the government gives you everything you want,
it can take away everything you have.

Adam76

November 04, 2021, 12:16:37 AM #66 Last Edit: November 04, 2021, 01:36:44 AM by Adam76
OK, figured it would at least cost me an hours labour for a compression test,  so I spent the money and bought a compression tester.

Results are interesting -
Front 180psi
Rear 190psi
I would have thought it be the other way around?

Are they about the numbers I should be expecting?

Thanks

kd

That much deviation could be a difference in the number of  cranking hits, the battery level ( which one tested first), a little wet residue, or a wet cylinder wall. No big deal at that percentage actually.  Try a dry and then wet test with a large (automotive) battery jumping it and see if they even up a bit.
KD

Don D

With those plugs run so short amount of time and the rear so dark I think you may have ring #2 upside down and that's oil not fuel discoloring the plugs. Pulling the pipes and looking in the exhaust port will tell the story.

hrdtail78

What intake and exhaust?  I have seen 90 degree air cleaners that do not play well with carbs.
Semper Fi

Hossamania

Quote from: hrdtail78 on November 04, 2021, 07:42:58 AM
What intake and exhaust?  I have seen 90 degree air cleaners that do not play well with carbs.

Post #57, std Arlen Ness Big Sucker
If the government gives you everything you want,
it can take away everything you have.

Adam76

Quote from: HD Street Performance on November 04, 2021, 06:26:51 AM
With those plugs run so short amount of time and the rear so dark I think you may have ring #2 upside down and that's oil not fuel discoloring the plugs. Pulling the pipes and looking in the exhaust port will tell the story.

Thanks HD, I'll pull the rear pipe and have a good look.

From checking the end of the rear muffler, it appears to be dry, black soot rather that wet oil.

I suppose dry black soot is better than wet dark oil?

I'm happy to pull the heads off and have a good look.... but I can't get another set of .030 Cometic head gaskets anywhere. Out of stock.

Thanks.


Adam76

Quote from: kd on November 04, 2021, 04:46:50 AM
That much deviation could be a difference in the number of  cranking hits, the battery level ( which one tested first), a little wet residue, or a wet cylinder wall. No big deal at that percentage actually.  Try a dry and then wet test with a large (automotive) battery jumping it and see if they even up a bit.

Thanks kd, I'll do another compression test later today.... what is a dry test vs a wet test?

Thanks

FXDBI

Quote from: Adam76 on November 04, 2021, 04:06:20 PM
Quote from: kd on November 04, 2021, 04:46:50 AM
That much deviation could be a difference in the number of  cranking hits, the battery level ( which one tested first), a little wet residue, or a wet cylinder wall. No big deal at that percentage actually.  Try a dry and then wet test with a large (automotive) battery jumping it and see if they even up a bit.

Thanks kd, I'll do another compression test later today.... what is a dry test vs a wet test?

Thanks

Wet test is done after the dry test. It involves putting a squirt or oil in the cylinder and doing the test. Hence the term wet. It will show if its ring or valve related by the readings. If it improves its rings no change look at the valves.   Bob

Adam76

Quote from: FXDBI on November 04, 2021, 04:44:20 PM
Quote from: Adam76 on November 04, 2021, 04:06:20 PM
Quote from: kd on November 04, 2021, 04:46:50 AM
That much deviation could be a difference in the number of  cranking hits, the battery level ( which one tested first), a little wet residue, or a wet cylinder wall. No big deal at that percentage actually.  Try a dry and then wet test with a large (automotive) battery jumping it and see if they even up a bit.

Thanks kd, I'll do another compression test later today.... what is a dry test vs a wet test?

Thanks

Wet test is done after the dry test. It involves putting a squirt or oil in the cylinder and doing the test. Hence the term wet. It will show if its ring or valve related by the readings. If it improves its rings no change look at the valves.   Bob

Thanks Bob  👍