New build - need help with CV40 carb set up please

[Adam76]

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

Bob, if it's valve related and I have to take the heads off.... that means a new set of has gaskets, right?
Finding a set of .030 Cometic head gaskets sent to Australia is proving very difficult.... Out of stock and on 6 month back order.

Cheers Adam

[Adam76]

Just checked the intake manifold for leaks..... no visible or audible sign of manifold leaks....

I'm tearing my hair out with this build.

Thanks again to all those who have helped and given advice.

Cheers

[Adam76]

Well it's all over now 

Started up the bike to check for exhaust leaks and then a lot grey smoke was coming  out the rear cylinder exhaust....

Shut it down and then checked the oil.  It was super frothy. Murky dark color and this was fresh oil I put in yesterday.

I think I've done the head gasket? But There's no sign around the base of the head where the gasket sits .... and the compression of the rear cylinder has dropped a touch  from 190 to 180psi.

This is going from bad to worse.

[Don D]

Before you rip into it check for sump oil.  Get it warm, idle for a few minutes, turn it off and remove the plug at the bottom of the crankcase. Measure how much oil comes out.

[harpwrench]

Right after shutting it off, remove the oil fill cap and listen for pressure escaping. I'm wondering if maybe you got the head breathers assembled incorrectly. If it's building pressure, it could be pushing oil into the chamber and cause at least a couple of your symptoms

[Don D]

 
Pulling the breather bolts while running there should be pressure released, if not I suspect the breathers assembled wrong or the under rocker box gasket backwards, usually blows off the cap with pressure

[Adam76]

Pulling the breather bolts while running there should be pressure released, if not I suspect the breathers assembled wrong
Thanks, I actually ran the bike the other day with no a/C and no breather bolts and the was plenty of pressure coming out both holes...

or the under rocker box gasket backwards, usually blows off the cap with pressure

Yes, I remember placing the rocker box gaskets the correct way.

[Adam76]

Right after shutting it off, remove the oil fill cap and listen for pressure escaping. I'm wondering if maybe you got the head breathers assembled incorrectly. If it's building pressure, it could be pushing oil into the chamber and cause at least a couple of your symptoms

Thanks Harpwrench, no pressurised oil filler cap...

UPDATE: 
Took the bike out for a good hour long run. These are the ONLY symptoms I'm getting.

1. Bike starts easy, runs well. No apparent loss of power.

* No intake or exhaust leaks

* Rear cyl has dropped in compression from 190psi to 175psi on compression test. but that could be my battery weakening. ?

2. I'm still getting quite a bit of light grey smoke out the rear cylinder exhaust.

3. Pulling the rear plug after a run, it's still black, almost a shiny sticky residue.

4. Front plug looks good.

5. Same black almost wet residue in the end of the rear exhaust muffler.

That's it, and when I pulled the rear spark plug immediately after the run there was a nice slow trail of smoke coming out the plug hole....

I'm starting to think I'll pull the rear head and replace the rings on the rear cylinder, and while I'm there get the valve guide seals checked, even though they were replaced during the build.

If you have any other suggestions, that would be great.

Rear plug -

[Don D]

If the rings didn't seat there will be visual signs. The second ring may be upside down, my original suspicion.

[-deuced-]

Couple of things -
First pic in this thread     Nice neat set up you've got there.
CV, your slide diaphragm looks ok in the pic. I pinched mine one time, the lip was not seated correctly. Bike started and ran ok but would not rev past 3000. It was obvious when I removed the carb top again. Checked carefully for holes or tears, none, so reinstalled correctly and all good. I don't think diaphragm is your problem but won't hurt to check.
Jets, if it was running good at 88" I would have used it as is to run in 95" but I don't think jetting is your problem.
Compression, I thought that should be done at WOT. Bit tricky on a CV to hold throttle grip on full and lift slide at same time. As previously mentioned the slide operates from vacuum when the engine is running. I'm not sure if your compression readings are accurate.
Rings, if one is installed upside down I would replace it. I think you might be ok there because you strike me as being pretty careful but it happens. I'm wondering about oil expansion ring. They are real easy to install wrong.

Pretty hard to tell from words on the internet about smoke issue on fresh build but I think it's going to cost you some gaskets.

Edit: btw that aerated oil in your tank is normal.

[Adam76]

If the rings didn't seat there will be visual signs. The second ring may be upside down, my original suspicion.

👍 thanks  -- stupid question but can I remove it and reinstall it in the correct way? Or do I need to get a new set of rings?
Thanks

[Adam76]

Couple of things -
First pic in this thread     Nice neat set up you've got there.
CV, your slide diaphragm looks ok in the pic. I pinched mine one time, the lip was not seated correctly. Bike started and ran ok but would not rev past 3000. It was obvious when I removed the carb top again. Checked carefully for holes or tears, none, so reinstalled correctly and all good. I don't think diaphragm is your problem but won't hurt to check.
Jets, if it was running good at 88" I would have used it as is to run in 95" but I don't think jetting is your problem.
Compression, I thought that should be done at WOT. Bit tricky on a CV to hold throttle grip on full and lift slide at same time. As previously mentioned the slide operates from vacuum when the engine is running. I'm not sure if your compression readings are accurate.
Rings, if one is installed upside down I would replace it. I think you might be ok there because you strike me as being pretty careful but it happens. I'm wondering about oil expansion ring. They are real easy to install wrong.

Pretty hard to tell from words on the internet about smoke issue on fresh build but I think it's going to cost you some gaskets.

Edit: btw that aerated oil in your tank is normal.

Thanks, appreciate your input. I think it's gong to cost me a set of gaskets.  😁 at the very minimum.
If the oil ring is installed upside down, can I reuse it by installing the correct way? Or do I need a new set of rings?
Thanks

[rigidthumper]

Pull the head/cylinder and inspect.
If the only issue is an upside down ring, I would just flip it over and reassemble.
I would reuse everything on my personal bike, but then again I have been accused of being a cheap/lucky SOB
If it leaks, then you're down yet again...

[Motorguru]

You have something wrong in carb. Not electrical issue.
Also, you should NEVER heat cycle an engine these days. You need to load it down almost immediately to properly seat rings. They seat in about the first 20-30 minutes. Miss that window and they never seat in.
Heat cycle and slow 500 mile is old school breakin method

[Don D]

I am in agreement about heat cycles. No idling, the freshly honed cylinders need oil and they get that better at a constant high idle 1500 or so and just a few minutes before getting it on the dyno to fix the mixture (EFI) or on the road for a carbed bike. Do not do any throttle blipping. Control the heat, do the break in in cooler weather. Third gear roll-ons up to 3500 rpm when the motor is warm. Do not use synthetic oil for break-in. A non-detergent oil such as Valvoline VR1 20w-50 or Shell Rotella 15w-40 are fine.

By the way, the new/used crank will need the timken clearance set. Follow the shop manual and it will take a few tools such as a dummy shaft and dial indicator, mag base, and bracket to mount that.

[Adam76]

Thanks Motorguru and HDstreetperformance,

It's good to get some clarification on how to properly do the break in on a new engine build.

Cheers. 

[Adam76]

By the way, the new/used crank will need the timken clearance set. Follow the shop manual and it will take a few tools such as a dummy shaft and dial indicator, mag base, and bracket to mount that.

Thanks, I'm guessing that my crank could be used as the dummy shaft to properly set up the timken clearance on the crank I'm going to put in?

[Don D]

When you read the manual it will be more clear.

[Motorguru]

I forgot to mention in my last reply. If you have a vacuum operated fuel valve, you fuel issue is likely a broken diaphram in the valve causing raw fuel to enter manifold.
Aoso, you can use old crank to set bearing clearance, however they make a tool for that which makes it very easy.

[Adam76]

I forgot to mention in my last reply. If you have a vacuum operated fuel valve, you fuel issue is likely a broken diaphram in the valve causing raw fuel to enter manifold.
Aoso, you can use old crank to set bearing clearance, however they make a tool for that which makes it very easy.

Thanks, Ill look into that.
Cheers

[Adam76]

I forgot to mention in my last reply. If you have a vacuum operated fuel valve, you fuel issue is likely a broken diaphram in the valve causing raw fuel to enter manifold.


I'm not sure if I have a vacuum operated fuel valve -- but I do have a MAP sensor on the intake manifold. 

[Hossamania]

Easy to see if it's vacuum operated, it will have a vacuum line! If it's oem, it is vacuum operated.

[Hossamania]

Also, that vacuum line is often a source of vacuum leaks.

[Adam76]

Easy to see if it's vacuum operated, it will have a vacuum line! If it's oem, it is vacuum operated.

Thanks Hoss,  yes standard vacuum like from carb to petcock.