Help needed getting this 750cc, 277 rephase running.

[Sacaps]

So let's start with a little history. I built this motor after building my first Tracker and was all hot to build a second hot rod and built this 750cc 277 rephased motor. A lot of other stuff then got in the way and this project has been in the corner for fourteen years. The lockdown/covid thing has now got me into the bottom of the project barrel and here we are.

Before I spend anymore time or money on it I thought I would get it running. Easy right? I hooked up an ignition, an IV bottle for fuel and can't get the right cylinder to fire.No amount of ignition checking, carburetor cleaning, valve checking has provided any success.
When it is running, it seems to be trying to blow out of the right carburetor rather than suck in. So I'm thinking valve timing. But if the left side runs then the right should follow since it is only one cam.
Remember the motor is rephased 277 degrees with the LEFT cylinder ahead of the right by 83 degrees.
So I think let's check the cam timing again. Anybody that has not done this, pay attention and anybody with some knowledge on the subject, show me were I am wrong.
First a degree wheel. and a positive stop for the piston on the side I want to check.

turn the crankshaft forward until it hits the stop, write down the number from the degree wheel. Turn the motor backwards until it hits the stop, Note the number. Top Dead Centre will be halfway between these two.
(be careful here as the valves are moving and the stop will damage the valves. On the XS motor if you back off completely the valve adjusters there will be clearance) remove the stop, turn the motor to the number halfway and you are at true Top Dead Centre.

Now since the opening of a valve is VERY slow, it is impossible to measure when it starts to move so a dial indicator is set onto the top of the valve and with NO valve lash (rocker to valve clearance) the opening of the valve is measured at .04" (1mm) or North American car guys use .050". I used .050"as this is what was specified in the cam timing chart.Note the number on the degree wheel, The is the valve opening value. It should be before top dead center.In my case I'm at 25 degrees before top dead center BTDC.Continue turning the engine forward until the dial indicator is an .050: and again note the number. Im at 45 degrees ABDC after bottom dead centre.

Now move the indicator to the exhaust valve and to the same. DO NOT MOVE THE DEGREE WHEEL.
I got Exhaust valve opening 50 degrees BBDC and closing at 20 degrees ATDC.
Now move to the left cytlinder and do the same.
Here are my readings
R/S Intake R/S exhaust L/S intake L/S exhaust
open 25btdc 50 bbdc 25btdc 47bbdc
close 45abdc 20 atdc 48 abdc 20 atdc

if you cant read it, the specs are 25 and 45 degrees for both the intake and exhaust. For this motor, that is as close as we are ever going to get.
Question 1.. is there anything wrong with the way I have installed the Cam?
Just for fun, while I had the degree wheel set up, I checked the opening of both the left and right side points opening.


with a spec of 15 degrees BTDC I would say I'm close enough.
Notes: if I swap coils and condensers left to right it makes no difference
New pistons, rings, and valves Compression in both sides is over 150psi
A timing light shows both cylinders firing.
So I have compression, spark at the correct time, cam timing correct and fuel I think
Question 2 ...Why wont it run?
I'm into one of those wrench throwing frustrating moments.
Anybody have a constructive idea?

 

[gggGary]

Is this your points set up? http://www.xs650.com/threads/bob-bertaut-277-points-ignition-conversion.57158/
I'm wondering if you are getting fire on the wrong stroke on the RH cylinder? Like Cliffo mentions TDC but the TDC when the valves are open. If you have 150PSI both sides the cam is certainly "close enough for it to run".

 

[Cliffo]

gary might be on to something, if you backed the tappets all the way out you might be on the wrong stroke and wouldn't have a way to quickly tell (loose tappets on compression) GET IT FIRED UP i want to hear it!

 

[Signal]

Rephasing can mess with your head.
Whenever I set up the cam on a rephased motor I only worry about the left side. The workshop manual method for installing the cam is all you need in most cases.
I have no experiance with points on rephased motors.
I do note that in your explanation you said that the left is ahead of the right by 83 degrees and it is however
I think it is more correct to regard the right piston as being 277 degrees behind the left. This may have no impact on your problem but it may help in your fault finding.

Edited: Comment incorrect

 

[Sacaps]

Thanks Gary. I have studied Bob's picture of his points setup in the past
.
For comparison mine's on the left here. What I don't understand about his setup is if the motor is (lets say a perfect 270) then the points should be at a 45 degree angle to each other. (the cam runs at 1/2 speed) His appear to be almost opposite each other. The big obvious difference is his right cylinder leads the left by 83 degrees and my left leads the right.
Your thought of the points opening on the top of the exhaust is valid. Not sure how to explain it but turning the motor by hand, and looking at the right intake valve, the motor approaches the top, the valve starts to open, the crank moves a full 360 degrees with the valve continuing to open until approaching bdc when it is closed. and the points open just before tdc with both valves fully closed. Seems correct to me. I will fire it up later and take a video.
Thanks for your help
Stephen

 

[Sacaps]

So just to go through the exercise to see if I have the points opening when the valves are open, 360 degrees out, we will start with the cam in a position were the points just opened. 15 degrees BTDC. I have the right side valve covers off and noting valve movement with my fingers.The first pictures shows an orange mark on the points cam were the points have just opened. At this point both valves are full closed.

the next is the exhaust starting to open and the intake closed

the next the exhaust valve starts to close

picture 5 the crank is at TDC the intake has started to open and the exhaust is almost closed

picture 6 has the intake fully open and the crank approx at bdc

the next both valves are fully closed

and we are back to the points open and two full rotations of the crank.

So I don't know how else to demonstrate but I sure that the points are opening at the correct time in the cycle.
How do I upload a video of it running?

 

[Sacaps]

try this
https://www.facebook.com/stephen.ab...00115772071&notif_t=video_processed&ref=notif

 

[gggGary]

How do I upload a video of it running?

You aren't far from the Canadian Mafia @MaxPete and @lakeview perhaps they could do some brainstorming?

 

[Steve C]

On mine, the right cylinder “leads” the left by 83*. When left piston is at TDC, right piston is in the middle of down stroke on its power stroke. I set the cam up using the stock marks with left piston at TDC. That puts the left cylinder at TDC of the exhaust stroke. Exhaust just closing, intake just opening. My cam is a Megacycle regrind, 250-20. Gary Hoos at Hoos racing helped me set everything up.
I’m using the Vape 277 PMA ignition rather than points. Seems like you just gotta walk through the cycles on each cylinder and verify your cam is phased correctly for the crank. Obviously makes a difference which piston is leading and that your cam is profiled correctly for your crank phasing. If you got valves starting to open at weird points in the travel of the piston, like intake begins to open with the piston halfway down the stroke, you prolly have a mismatched crank/cam combo.
Hope this helps, good luck!

 

[Sacaps]

Thought that what was the whole explanation at the start of this thread. Which piston leads doesn't matter if the valves for that cylinder open and close at the right time and the spark happens correctly. Read through my setup from the beginning and 1- tell me what more information you need and 2- where or what am I missing?
Thanks.

 

[Steve C]

Yes, I read it. And wanted to explain how my 277 motor was set up because it sounds like yours is different. My understanding is that 277 cranks are usually set up with right cylinder ahead of left 83*. Or as Signal said, right is 277* behind left is a better way to think of it. Firing order should be left cylinder first, then 277* later right cylinder fires. But if your right cylinder is only 83* behind the left, the cam & ignition needs to be set for that phasing. What cam are you using? If you timed the cam with stock cam mark at 12 o’clock and left cylinder at TDC and That cylinder fires and runs, then there’s something wrong with the cam timing for the right cylinder. Which piston leads does matter and the cam phase & iggy has to match the crank phasing.

 

[Steve C]

Ok, re read again and I guess I’m back to; Are the points working right? 12v test light clipped to wire to points. Other end to ground. Points closed, light should be fully off, not dim, not flickering...off. Points crack open and light should come on bright. When points just open is when high voltage is released from coils to jump the spark gap. You swapped coils and condensers, you try swapping the points yet? Gotta make sure they are closing & opening.

 

[Oldnwiser]

I really hope that you got it running. Points are always better than electronic when diagnosing an issue. They rarely fail and the times they have turned out to be the condenser.

 

[Sacaps]

So, I forgot about this post. Let me fill you in. Someone commented about the cool little stubby mufflers. I said they were straight through and that a piece of wire inserted through them would go right to the exhaust valve. Hmmm I wonder. A piece of welding rod stops halfway up the pipe. WTF?
I cut the pipe open. Anybody ever seen this?
I cut the collapsed piece out, welded the pipe back together and….

 

[Niels B]

I really hope that you got it running. Points are always better than electronic when diagnosing an issue. They rarely fail and the times they have turned out to be the condenser.

I just had the rare occasion where the point to my left cylinder failed - I was dumbfound and it caused me a lot of trouble to identify

 

[gggGary]

So, I forgot about this post. Let me fill you in. Someone commented about the cool little stubby mufflers. I said they were straight through and that a piece of wire inserted through them would go right to the exhaust valve. Hmmm I wonder. A piece of welding rod stops halfway up the pipe. WTF?
I cut the pipe open. Anybody ever seen this?
I cut the collapsed piece out, welded the pipe back together and….

Not common but a collapsed inner pipe has been reported a few times, very tough to diagnose!
One theory is water gets in the vent holes and freezes, over many freeze thaw cycles it pushes the inner pipe in.

 

[Oldnwiser]

I just had the rare occasion where the point to my left cylinder failed - I was dumbfound and it caused me a lot of trouble to identify

That is unusual, it’s usually a condenser or a ground wire that is broken.

 

[Raymond]

Coo - that's a new one for me, collapsed inner pipe. No wonder Stephen was ready for throwing wrenches.