[teacher]

imported post

Hi,

I'm in need of help on a 1981 GL1100. First let me say that I rebuilt this engine and put it back in the frame. I tried starting it and nothing. I did all the test, compression, fuel, electrical, and ignition. All of these were positive. So, by reading the service manual I figured it was out of time. I begain by lining up the T1 mark located at the top back of the engine block. Then checking the timing marks on each cam (left and right) and they line up perfect!

Every time I tried to start the engine I would try to start then backfire.

A machanic friend of my told me that I could be 180 degrees out of time. So I begain.

First, I lined up the T1 mark, then took the belt off the left cam. I then turn the crank clockwise until the T1 mark came up again; reconnected the left cam belt and tried to start the engine. Nothing but a lot of backfires. I did the same to the right side. and nothing.

After several tries at this the engine sounded different. Freewheel, no back pressure.

So I checked the compression and had none. I just don't know where to turn now.

I've continue try to put in time thinking I'll get compression once I have back in time.

I've been at it for 2 days and now It's time to ask for help.

thanks, teacher

 

[twisty]

imported post

teacher wrote:

Hi,

I'm in need of help on a 1981 GL1100. First let me say that I rebuilt this engine and put it back in the frame. I tried starting it and nothing. I did all the test, compression, fuel, electrical, and ignition. All of these were positive. So, by reading the service manual I figured it was out of time. I begain by lining up the T1 mark located at the top back of the engine block. Then checking the timing marks on each cam (left and right) and they line up perfect!

Every time I tried to start the engine I would try to start then backfire.

A machanic friend of my told me that I could be 180 degrees out of time. So I begain.

First, I lined up the T1 mark, then took the belt off the left cam. I then turn the crank clockwise until the T1 mark came up again; reconnected the left cam belt and tried to start the engine. Nothing but a lot of backfires. I did the same to the right side. and nothing.

After several tries at this the engine sounded different. Freewheel, no back pressure.

So I checked the compression and had none. I just don't know where to turn now.

I've continue try to put in time thinking I'll get compression once I have back in time.

I've been at it for 2 days and now It's time to ask for help.

thanks, teacher

Teacher, unfortunately it's possible you might have bent the valves by cranking it withthe cams timed incorrectly. You REALLY NEED TO ALWAYS turn the engine over a couple of revolutions BY HANDafter ANY cam belt replacement or movement. IF, you had or now have it (cams)mis-timed by 180° you probably didn't bent a valvebut any other place could be fatal for valve life.

PUT IT EXACTLY in cam timing as the the book calls for & re-try the compression check & hope that is all that is wrong withthe compression.

First, I lined up the T1 mark, then took the belt off the left cam. I then turn the crank clockwise until the T1 mark came up again; reconnected the left cam belt and tried to start the engine. Nothing but a lot of backfires. I did the same to the right side. and nothing.

That crankshaft was turned 360° so the pistons were right back where you started. The crankshaft only knows ONE position for TDC no matter how many times you turn it as long as the timing mark lines back up. BUT the CAMS can be off to the pistons if they aren't also moved to line up when the crank is lined up with it's timing mark.

With any luck you now just have BOTH cams off 180° & that probably didn't bend a valve as that is a normal place to end up. Both cams off 180° will give you 0 compression.

I guess if you suspect bent valves pull all 4 spark plugs, then remove the valve covers & make sure the valves are closed on one cylinder at at time, then blow compressed air into that cylinder through the plug hole& see if the air comes out either the intake or exhaust,, if so you bent a valve on that cylinder.



Twisty

 

[teacher]

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Thanks guys,

To do a proper check. Can you tell me where the #1,2,3, and 4 cylinders are as you face the the front of the bike?

 

[twisty]

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teacher wrote:

Thanks guys,

To do a proper check. Can you tell me where the #1,2,3, and 4 cylinders are as you face the the front of the bike?

Teacher, sitting on the seat the #1 is the front on the brake lever side,, #3 is the rear on the brake lever side,, #2 is the front on the shifter side,, #4 is the rear on the shifter side.

Twisty

 

[Goldwinger1984]

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Any luck with it yet Teacher?

Vic

 

[teacher]

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hey twisty,

Thank you very much. I read everything I can read and asked everyone I know to ask. Know where #1,2,3 &4 is a great, great help. Thanks again! Teacher

 

[jackjohn]

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Hi Teacher, I'm about 14 miles up the road if you need hands on help.

 

[teacher]

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hey jack,

I sure could use some help on this one. I can usually figure things out but I really don't understand valves and lifters and pistons. But give me a carb and I can fix it.

Send me an email at: [email protected] and hopefully we can put two heads together and get me back on the road. Thanks again Jack. Teacher

 

[teacher]

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hi vic,

With all the response at least I have a start. I'm going to try some things twisty said and others. I'm even checking on price of valves. At least I have some direction. Thanks for the inquire. Teacher

 

[Goldwinger1984]

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Sounds like you may have found a willing helper.

Keep in mind that if the valves are bent that it may be cheaper to find a set of used heads as Honda's prices are outrageous on the these types of parts.

Hopefully it'll just turn out to be a cam timing issue.

Vic

 

[twisty]

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Teacher, if you get a chance & have the means take an old spark plug &break out the center electrode, then weld or braze in an air hose fitting that will fit your air compressor hose. That (special plug) will be a big asset in pressurizing the cylinders tocheck for a "leakdown" condition due to bent valves or other problems. That lack of compression really has to be addressed before it will even have a chance of starting.

Twisty

 

[teacher]

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hey twisty,

Thanks for the tip! I was just about to go outside and try the tips on compression you gave me last night.

Teacher

 

[teacher]

imported post

hey twisty,

If I line up the T1 mark on the crank.... then, line up the Right and Left cam on their mark.....then, take the belt off the, say, right cam.....then turn the crank until the T1 mark lines up again....then put the belt back on the right cam will the right cam and crank be in time or maybe 180 out of time?

teacher

 

[Goldwinger1984]

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CAUTION: If you turn the the cam or crank more than a few teeth you stand a good chance of damaging valves. If I were in your position at this time I would seriously consider removing the rocker arms to prevent bending any valves, then get the cams and crank lined up and timedcorrectly, then reinstall the valve gear.

Vic

 

[teacher]

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hey vic,

Wow! Thanks for that I was just about to get started.I'll take the rocker arms off first. Thanks, teacher

 

[Goldwinger1984]

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You're welcome Teacher. I'd sure hate to see you make an expensive mistake.

Hopefully none of your valves are bent already and it was just a timing issue causing the problem.

Good luck and keep us posted.

Vic

 

[twisty]

imported post

teacher wrote:

hey twisty,

If I line up the T1 mark on the crank.... then, line up the Right and Left cam on their mark.....then, take the belt off the, say, right cam.....then turn the crank until the T1 mark lines up again....then put the belt back on the right cam will the right cam and crank be in time or maybe 180 out of time?

teacher

Teacher, once the T1 mark is lined up turning the crank again gains you nothing. That crank (& pistons) are ALWAYS in the same place at T1 regardless of how many times you turn it. Now once the cam belts are hooked up the crank to cam position can change if the crank is turned with only one belt hooked up. Basically BOTH cams should be timed to their marks with the crank at TDC.

Be careful when turning the crank or cams with the belts removed,, do all turning by hand & if resistance is felt turn the cam(s) a little until you don't hit resistance. The cams can be lined up without pulling the rockers but you must be careful not to force the crank or cams past any resistance. If you (can) turn the crank to TDC (#1) then back it up about 1/4 turn that will allow the valves to clear the pistons as you rotate the cams.


Twisty

 

[Goldwinger1984]

imported post

Teacher, all it takes is for the piston to contact the valve slightly and you will then lose compression and will need to replace bent valves to get the compression back up.

If you know exactly where the valves are in relation to the pistons and money is no object to you go ahead and spin the crank until the pistons touch the valves, but, from what I've read so far in the posts it sounds like you may be uncertain about the cam to crank timing. Removing the rockers will give you great lattitude to experiment and get it right without risking anything except the time to remove the valve covers and valve gear.

Vic

 

[twisty]

imported post

Goldwinger1984 wrote:

Teacher, all it takes is for the piston to contact the valve slightly and you will then lose compression and will need to replace bent valves to get the compression back up.

If you know exactly where the valves are in relation to the pistons and money is no object to you go ahead and spin the crank until the pistons touch the valves, but, from what I've read so far in the posts it sounds like you may be uncertain about the cam to crank timing. Removing the rockers will give you great lattitude to experiment and get it right without risking anything except the time to remove the valve covers and valve gear.

Vic

Teacher, if you do pull those rockers that would be an ideal time to pressurize the cylinders with compressed air to check for valve leakage as ALL valves will be closed. If valve leakage is present no need to go farther on cam timing as it will have to come apart anyhow.

Twisty

 

[gaswing]

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Twisty has been very thorough and probably covered it all here, it does look like you bent some valve. The giveaway is when you took a belt off and turned the engine completley until the T1 mark came up. You shouldn't have been able to do that without one of the pistons locking up against a valve. I'd say some valves were already bent by that atage.