ST1100 No compression

WyzzardST · Jul 20, 2016

Hello fellas and ladies,

last week the bike quit on me en route to work though and I saw it was dropping some oil, the viscosity was thin as if there was fuel in it, though I am unsure. The starter motor just spun and spun and my mechanic said there was no compression. the mechanic has been unable to get to it being that it is peak season. Does anyone have suggestions on the cause and maybe some tips about troubleshooting, I'm gonna start disassembling this week at a motorcycle co-op garage in SANfrancisco so I will have all tools at my disposal ...

1990
67k

bought 2months ago put on 2500 miles, unsure of valve clearances prior to issue...

dwalby · Jul 20, 2016

what do you plan on disassembling?

your first step would be a compression measurement, to see exactly where your compression values are before going any further.

If the co-op garage doesn't have one available, you can borrow a compression tester from AutoZone for free if you leave a deposit.

Mcreviver · Jul 20, 2016

Where is the oil coming from? Head gasket?

Slydynbye · Jul 20, 2016

Are you going to Motoguild on Treasure Island? If so I might be able to drop by and help or at least Kibitz.

dkruitz · Jul 21, 2016

Definitely do some basic troubleshooting before tearing into it. Losing compression on ALL cylinders would be very strange imho.

schlep1967 · Jul 21, 2016

With no compression, a 26 year old bike that has not reached the "recommended" 90K mile timing belt change interval, my first guess would be timing belt. And if that went you are not going to like the repair costs.

wjbertrand · Jul 21, 2016

dkruitz said:
Definitely do some basic troubleshooting before tearing into it. Losing compression on ALL cylinders would be very strange imho.

Agree. I lost all compression on cylinder #4 of my ST1100 due to a burnt exhaust valve, the bike still ran but with the distinct feeling there was some dead weight being swung around. Once you've done a compression check, put each cylinder on top dead center compression stroke, remove the plugs and pipe some air into the plug hole, slowly. Put the bike in gear and hold the brake pedal if necessary to prevent the engine turning over. While air is flowing listen at the end of the exhaust, the air cleaner intake and at the oil fill hole to see if you can hear the air. This will give you a clue as to what is wrong.

schlep1967 said:
With no compression, a 26 year old bike that has not reached the "recommended" 90K mile timing belt change interval, my first guess would be timing belt. And if that went you are not going to like the repair costs.

This makes a lot of sense and is the only way to explain loosing compression on all four cylinders at once and so suddenly. A snapped belt and slipped timing can cause all four valves in each cylinder to be bent and therefore not seat, i.e. no compression.

Grabcon · Jul 21, 2016

Pull the valve covers and check your valve clearance. This happened to me on my 1991. Tight valves would not run. I was fortunate and did not burn any valves. But I did have to go through to 2 rounds of adjustment as I had no baseline since the valves were so tight that a 0.0015" feel gauge would not fit between cam and valves.

One other note here. If the valve clearance is excessive you may have carbon build up holding the valves open, increasing the clearance. Either way it can result in lost compression.

schlep1967 · Jul 22, 2016

wjbertrand said:
Agree. I lost all compression on cylinder #4 of my ST1100 due to a burnt exhaust valve, the bike still ran but with the distinct feeling there was some dead weight being swung around. Once you've done a compression check, put each cylinder on top dead center compression stroke, remove the plugs and pipe some air into the plug hole, slowly. Put the bike in gear and hold the brake pedal if necessary to prevent the engine turning over. While air is flowing listen at the end of the exhaust, the air cleaner intake and at the oil fill hole to see if you can hear the air. This will give you a clue as to what is wrong.

This makes a lot of sense and is the only way to explain loosing compression on all four cylinders at once and so suddenly. A snapped belt and slipped timing can cause all four valves in each cylinder to be bent and therefore not seat, i.e. no compression.

Either the timing belt or somebody stole all of your spark plugs while you were riding down the road.

Al st1100 · Jul 22, 2016

Quit while running eliminates carbon build up or valve clearance. Was running fine and quits means catastrophic failure maybe. If the motor cranks over and sound like its just spinning open the oil cap and see if the cams are turning while cranking.. plus 1 on timing belt,

Oldbikefixr · Jul 22, 2016

Al st1100 said:
Quit while running eliminates carbon build up or valve clearance. Was running fine and quits means catastrophic failure maybe. If the motor cranks over and sound like its just spinning open the oil cap and see if the cams are turning while cranking.. plus 1 on timing belt,

I had this happen on a GL1000 I had restored. The failed left side timing belt was just a few years old and shed some teeth (Gl's had two belts, one right, one left). No noise, no clattering, no drag, it just shut off. Postmortem revealed four slightly bent exhaust valves...no compression.

The belts were from a distributors stock, two years installed, yet one experienced age related failures. No telling how long the belt had been sitting in the warehouse, could have been as long as 35 years at that point. Yes, it was aftermarket. I bought it because I knew Honda belts were long out of production and what I could get was either NOS or from an aftermarket house.

This is something we ST1100 owners should be aware of when the new manufacture Gates belts dry up.

John OoSTerhuis · Jul 22, 2016

Remove the little timing inspection cover. Whaduhyah see?

John

Brant · Jul 22, 2016

dwalby said:
what do you plan on disassembling?

your first step would be a compression measurement, to see exactly where your compression values are before going any further.

If the co-op garage doesn't have one available, you can borrow a compression tester from AutoZone for free if you leave a deposit.

+1!.........just cause some supposed mechanic states it cranks over reasonably fast and no igniting sure has nothing to do with throwin' out a guess like that. That in itself would steer me elsewhere

.

WyzzardST · Jul 27, 2016

Thanks guys I'll look in to the timing belt and if that's stil intact then I'll check compression. By the sounds of it I'll be tackling this in my buddy's garage in alameda. I don't want to front the cash at Moto guild in case I get a multi-week project handed. To me :-(

thanks again!

WyzzardST · Jul 27, 2016

schlep1967 said:
Either the timing belt or somebody stole all of your spark plugs while you were riding down the road.

Love this. Hope they're there and that I need a new belt!

Brian Lamberts · Jul 30, 2016

schlep1967 said:
With no compression, a 26 year old bike that has not reached the "recommended" 90K mile timing belt change interval, my first guess would be timing belt. And if that went you are not going to like the repair costs.

!!! +1

Is the ST1100 engine an interference engine? Pistons hitting open valves bends the valves. Not a good thing. If it were my engine, I'd be debating whether to have the heads worked or to buy a replacement engine. There seem to be a lot of good used engines on Ebay for not much money.

wjbertrand · Jul 30, 2016

Brian Lamberts said:
!!! +1

Is the ST1100 engine an interference engine? Pistons hitting open valves bends the valves. Not a good thing. If it were my engine, I'd be debating whether to have the heads worked or to buy a replacement engine. There seem to be a lot of good used engines on Ebay for not much money.

Yes it is an interference design. There are a couple reports of broken, shredded timing belts, jumped timing and in one case 16 bent valves.

-Jeff

WyzzardST · Jul 30, 2016

JFairings are off, just found out the leak was coolant. It's almost black, thus my thoughts on oil...

Looked in the oil fill cap while trying to start and nothing is moving... Hoping it's the main belt and/or tensioner

I'll keep y'all updated.

WyzzardST · Jul 30, 2016

Got the covers off. Shredded rubber all over the place. New t325 is ordered and waiting to install. Once I get it back on, does anyone have other tips on alignment of pulleys or other maintenance?

Im going to have the radiator cleaned at a shop and I'll flush the reservoir (likely even drain cylinder coolant??)
Also changing oil of course...

70,128 miles
suggest water pump?
Other suggestions?

schlep1967 · Jul 30, 2016

Before anything else you need to check if the valves are bent. It may be more cost effective to replace the motor.

ST1100 No compression

WyzzardST

dwalby

Mcreviver

Slydynbye

Will ride for Pie

dkruitz

schlep1967

Bill

wjbertrand

Ventura Highway

Grabcon

schlep1967

Bill

Al st1100

Oldbikefixr

John OoSTerhuis

Life Is Good!

Brant

WyzzardST

WyzzardST

Brian Lamberts

STOC 8845

wjbertrand

Ventura Highway

WyzzardST

WyzzardST

schlep1967

Bill