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TOPIC: Re:Firing on one cylinder
#1020695
Paladin (User)
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Re:Firing on one cylinder 6 Months ago  
Ctkog wrote:
Before going and getting another engine make sure you've got an accurate read on that compression. It sounds like you may not have. if your decomp solenoid was activating during the check, pressure will read low, if the tapered rubber test line is not firmly seated, it will read low. Make sure the decomp solenoid is completely out of the loop, and maybe get some help holding the rubber line on good.

The black buildup could have been simply from running a while with the bad lifter, the rich gases burning and not expelling properly.

If your compression IS good you might only be looking at a cam and lifters which is a much smaller bite to chew off than an engine swap. I'm just saying,.. be sure before you assume you need a motor, that's all.

If you don't need one you may find someone on this forum that has a stock cam and lifters laying around from upgrading to a performance cam. You never know.


Am I thinking right that I can't do the compression test right now because it would get everything out of time with the lifter & push rods out of the front cylinder?
 
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#1020697
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Re:Firing on one cylinder 6 Months ago  
Paladin wrote:
Ctkog wrote:
Before going and getting another engine make sure you've got an accurate read on that compression. It sounds like you may not have. if your decomp solenoid was activating during the check, pressure will read low, if the tapered rubber test line is not firmly seated, it will read low. Make sure the decomp solenoid is completely out of the loop, and maybe get some help holding the rubber line on good.

The black buildup could have been simply from running a while with the bad lifter, the rich gases burning and not expelling properly.

If your compression IS good you might only be looking at a cam and lifters which is a much smaller bite to chew off than an engine swap. I'm just saying,.. be sure before you assume you need a motor, that's all.

If you don't need one you may find someone on this forum that has a stock cam and lifters laying around from upgrading to a performance cam. You never know.


Am I thinking right that I can't do the compression test right now because it would get everything out of time with the lifter & push rods out of the front cylinder?


Your valves should still be closing (or be closed) which will give you a compression read, even with the bad lifter. It's opening it can't do. Maybe someone else knows better and wants to chime in here.
 
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#1020700
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Re:Firing on one cylinder 6 Months ago  
With the cam still installed it won't get anything out of time. You won't be able to do a test on the front cylinder but you could the rear if the pushrods are still in place. And if the carburetor is off it'll be easier. You can remove the left cover and disconnect the solenoid wire (not the thermistor wire) or just unbolt the solenoid - easier.

The front cylinder valves will just remain closed which is handy for a leak down test.
 
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#1020705
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Re:Firing on one cylinder 6 Months ago  
+1 on leakdown check... sorry I didn't realize your valves were staying closed completely and not opening at all.

You should be able to rent a leakdown tester from an auto parts store. Would be ideal if you could do this check to know for sure which direction to go next on your bike.

(Below is copied info on leakdown test for you)

An engine leakdown test is a compression test in reverse. Instead of measuring the engineís ability to create pressure, compressed air is introduced into the cylinder through the spark plug hole. One gauge on the tester measures the pressure of the air entering the cylinder and the other measures the percentage of the air escaping (or leaking) from the cylinder. The loss percentage will indicate the condition of the cylinder and overall condition of the engine.

Before sending air into the engine, the cylinder being tested must be placed at Top Dead Center (TDC). The piston must be at the top of its travel. The intake and exhaust valves must be closed. When the air is compressed into the cylinder, the leakdown tester will measure any loss of air escaping past valves or piston rings. If the cylinder is not at TDC, air escaping past an open valve will give a false reading.

No engine will have perfect sealing with 0 percent loss. Five to 10 percent loss indicates an engine in great to good running order. An engine between 10 and 20 percent can still run OK, but itíll be time to keep an eye (or ear) on things. Above 20 percent loss and it may be time for a teardown and rebuild. Thirty percent? Major problems. The percent of leakage should also be consistent across the cylinders. Any great differences indicate a problem in that cylinder.
 
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Last Edit: 2017/08/27 18:18 By ctkog.
 

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#1020725
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Re:Firing on one cylinder 6 Months ago  
OK, thanks for the info. So by bumping the starter I move the pistons to TDC. Once there, both the intake and exhaust valves (assuming I'm on the rear cylinder) should be closed and I should be able to perform the leakdown without any problem? I guess I could do the compression test first just to get that out of the way and then do the leakdown. Going back to the front cylinder, The intake valves are closed completely already since they weren't working but I wouldn't have any control over the exhaust valves since the pushrods and lifter are out, so I can't do compression or leakdown on that cylinder, correct? Thanks again, really appreciate the help!!
 
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#1020745
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Re:Firing on one cylinder 6 Months ago  
Paladin wrote:
OK, thanks for the info. So by bumping the starter I move the pistons to TDC. Once there, both the intake and exhaust valves (assuming I'm on the rear cylinder) should be closed and I should be able to perform the leakdown without any problem? I guess I could do the compression test first just to get that out of the way and then do the leakdown. Going back to the front cylinder, The intake valves are closed completely already since they weren't working but I wouldn't have any control over the exhaust valves since the pushrods and lifter are out, so I can't do compression or leakdown on that cylinder, correct? Thanks again, really appreciate the help!!

You should be able to do the leakdown check on the front cylinder also. Even with the pushrods and lifters out the valve springs keep the valves closed. TDC will occur after you see the intake valve close and the piston reaches the top. The front cylinder TDC shouldn't matter since you said the valves are not opening. But just to be sure you should probably place the front cylinder on TDC too when checking it.. because if the fronts are opening at all you'll have a problem with the check if not on TDC.
 
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Last Edit: 2017/08/28 13:00 By ctkog.
 

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#1020747
Paladin (User)
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Re:Firing on one cylinder 6 Months ago  
Ctkog wrote:
Paladin wrote:
OK, thanks for the info. So by bumping the starter I move the pistons to TDC. Once there, both the intake and exhaust valves (assuming I'm on the rear cylinder) should be closed and I should be able to perform the leakdown without any problem? I guess I could do the compression test first just to get that out of the way and then do the leakdown. Going back to the front cylinder, The intake valves are closed completely already since they weren't working but I wouldn't have any control over the exhaust valves since the pushrods and lifter are out, so I can't do compression or leakdown on that cylinder, correct? Thanks again, really appreciate the help!!

You should be able to do the leakdown check on the front cylinder also. Even with the pushrods and lifters out the valve springs keep the valves closed. TDC will occur after you see the intake valve close and the piston reaches the top. The front cylinder TDC shouldn't matter since you said the valves are not opening. But just to be sure you should probably place the front cylinder on TDC too when checking it.. because if the fronts are opening at all you'll have a problem with the check if not on TDC.


Makes sense. I guess with the push rods out, both the intake and exhaust valves would be held shut by the valve springs - wasn't thinking about that. I can stick a straw or something in the spark plug hole to watch the piston and make sure it's a TDC or as close as I can get it. Thanks.
 
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#1020748
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Re:Firing on one cylinder 6 Months ago  
Paladin wrote:
I can stick a straw or something in the spark plug hole to watch the piston and make sure it's a TDC or as close as I can get it. Thanks.

Yep a straw is great and you really just need to be close on TDC for this check, not absolutely dead on.

I hope your leak down results are favorable Paladin. There are plenty guys on this forum with tons of experience (more than me) so don't hesitate to ask for more advice or help if you feel stuck or unsure.
 
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#1020752
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Re:Firing on one cylinder 6 Months ago  
Thanks, I really do appreciate your - and everyone's - help, it's proving to be invaluable. I've been riding and working on my own bikes for 47 years now and while I can do a little more than most people, I still don't have anywhere near the knowledge you guys have. I'm worried about some of this is above my level of expertise, but I'm more worried about accidentally messing something up because of what I don't know. Like for example the compression test. Everyone said to do a compression test so I borrowed a tester, stuck it on there, and cranked the motor until the pressure maxxed out. What I didn't know was that I was supposed to have disconnected the decomp solenoid (which makes sense now that I think about it) and hold the throttle wide open (which I still don't understand). So I just need to make sure I ask a lot of questions and I hope they don't seem dumb. I'm sure I can do this stuff, but I just need to make sure I don't get ahead of myself and skip some important step Thanks again!!!!!
 
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#1020756
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Re:Firing on one cylinder 6 Months ago  
Paladin wrote:
Thanks, I really do appreciate your - and everyone's - help, it's proving to be invaluable. I've been riding and working on my own bikes for 47 years now and while I can do a little more than most people, I still don't have anywhere near the knowledge you guys have. I'm worried about some of this is above my level of expertise, but I'm more worried about accidentally messing something up because of what I don't know. ........ So I just need to make sure I ask a lot of questions and I hope they don't seem dumb. I'm sure I can do this stuff, but I just need to make sure I don't get ahead of myself and skip some important step Thanks again!!!!!

Feel free to PM me if you think a question is redundant. There are no dumb questions except the ones we don't ask. The good thing about compression checks and the leakdown test is you can't really screw up your bike since you're not getting into timing or anything tricky at that point, simply spinning the engine. So proceed fearlessly.

Like for example the compression test. Everyone said to do a compression test so I borrowed a tester, stuck it on there, and cranked the motor until the pressure maxxed out. What I didn't know was that I was supposed to have disconnected the decomp solenoid (which makes sense now that I think about it) and hold the throttle wide open (which I still don't understand).

Yeah the decom solenoid aids in easier engine starting by bleeding off some cylinder pressure when the starter button is depressed. So obviously if it's activating it will throw your compression check to the low side. When you take the throttle wide open I believe it's the TPS that tricks the decom solenoid to deactivate and provide full cylinder pressure for the test. Hope that explains it ok.
 
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