Low compression: 115 psi vs. 170 psi

[Mean Wing]

I'm extremely challenged when it comes to automotive tasks & knowledge. However, I was able to run a compression check on my 1978 GL1000 (with only 16,000 miles) and found all four cylinders registering @ 115 psi. The Honda Service Manual states that "170 psi is normal, while any reading below 140 psi is indicative of a leak or an engine needing a complete overhaul.

Any other thoughts or ideas before give up hope?

Chet

[chrisz]

Ride it for several weeks (daily hopefully) and remeasure. Then come back and let us know the new/improved numbers... The fact that the pressures are very close together has a glimmer of hope...

[ct1500]

What problems are you experiencing with the engine?

[Aussie81Interstate]

With 16000 miles it is hardly worn in - could be stuck rings - or valve adjustment that is out.

[maintainer]

I agree, at 16K miles there will be no need for an overhaul. At that kind of ultra low mileage it must have sat a lot. I agree with the previous post. Dose it with an oil change and use about 3 quarts of any oil of your choice and 1/2 quart of Marvel Mystery Oil. Ride the wheels off and that should free up any stuck rings. It could be a valve lash problem out of adjustment but I would suspect that less than stuck rings.

[Mean Wing]

Based upon the responses, it appears that all might not be lost. I've not had any issues with the bike, per se. Starts right up. Idles and runs with no problems. I've been averaging 40 mpg. But, since I have no previous GL1000 experience (bought this '78 this past June) , I have nothing to compare to when it comes to pickup, torque, power, etc. It seems to take 3,000-4,000 rpm to get things going, unlike my GL1800 at just over 2,000 rpm. Not sure if that's normal . . .

But, the Carb set has been removed and is off to Pistol Pete's for a complete rebuild, so this is the time to start in on the engine. I'll dive into the Service Manual and start with the Valve adjustment procedure and see if I get anywhere. With my extremely limited experience, I dread going all the way to replacing the piston rings. I'm not even sure where to buy a set these days.

Thanks for your responses! I need all the guidance and encouragement I can muster . . .

[maintainer]

You can't compare an 1000 to an 1800s power delivery. I have owned both too.
The 1800 makes bags of torque and power down low and red lines at just over 5000 (ultra low revver)
The 1000 makes power from midrange up and red lines at about 8000 rpm. (moderately high revver)
Two different animals

[Fatwing Chris]

If it works as good as you say it does then I would say your only problem is with the compression test itself.Whether the gauge is off or maybe it wasn't performed properly.I've had every size of Wing and all of them except the 1800 are pretty lazy under 3000 rpm.It idles good and you're getting 40 mpg?Sounds like it's running pretty good.If it were me I'd just drive and enjoy it.

[Mean Wing]

Sounds like I might be overthinking all of this (signs of a "Newby"). New game plan: Take a "chill pill," get my Rebuilt carbs back, buy some Marvel Mystery Oil, and ride, ride, ride . . .

Thanks, guys!

[Mean Wing]

One last thing while I'm at it: What's the trick for removing these annoying ads that accompany my posts?

[WingAdmin]

One last thing while I'm at it: What's the trick for removing these annoying ads that accompany my posts?

It depends. Do you like using this site? Because those annoying ads are what pay for the costs entailed in running it.

[Mean Wing]

Oh, I was only afraid of annoying my responders, as a new guy. If it pays the bills, then I'm good!

[wingman12]

Good afternoon mean wing, welcome to this site, I did not notice if you mentioned that you had any repair history for your new project wing. I also noticed that nobody mentioned that if no repair history it is a good idea to replace the timing belts while you have the carbs out for overhaul. you might as well check many engine related areas while you are at it, such as thermostat, both radiator hoses, is there any fluids coming out of the water pump weep hole. Other areas to look at are, how are the wheel bearings, how about the condition of the brakes and calipers, how old are the tires, a old girl like you got has sat a lot more that been driven, sitting causes lots of mechanical failures as you start using the bike, preventative maintenance while down goes a long way in preventing breakdowns when you are away from home on a pleasant days ride.

[Ncscooter]

Also, did you have the throttle open as you checked compression? If it runs well, I wouldn't worry. Mileage indicates it's fine. I would address the things mentioned above and certainly change the belts!

[WINGER3]

If compression rely is 115 psi on all 4 cyl. then it should take a long time cranking it to get it to start. Also it would have very low power and do a lot of stalling on take off and MPG would be very low. I would say that the gauge you are using is leaking, if the needle stays at 115 psi until you release it, it's good, if it leaks down then its bad. From what you say about the bike it sounds like it is running great and I would not worry about the compression. Do replace the timing belts before any more rides. if you don't know when they where replaced, if ever, age destroys them not miles.

[Mean Wing]

Thanks for all the great advice! Here's what I do know for sure:
1. The Compression kit was purchased at Harbor Freight solely for this test. The gauge on the first kit (a less expensive one) failed on the second cylinder tested, so I took it back. The second kit ($29, of slightly better quality) held the pressure and gave me readings of 115 psi all the way around. I guess it's still possible that the U.S. General brand of gauge is inaccurate or cheaply made and gives false readings.
2. With the motorcycle disassembled to the stage it's in, I'm already feeling like I've bit off more than I can chew, however, I'll take your advice and look into new timing belts and read about this process. It makes sense to me. I'm hoping that I don't have to remove the radiator, though.
3. With the Carb set gone, looking into the Valve ports I can see what I assume is carbon (or sludge) buildup on the back side (curved portion) of each valve. Over time, will a product like Marvel Mystery Oil take care of this?
4. Due to the position (proximity to the frame cross bar) and age of the bike, I'm having no luck removing the Generator Bolt Cap (17mm) with my socket wrench. I'll check the stores for a 17mm open end wrench or some kind of "offset" tool that may work.
Now if I could just eliminate having to go to work on a daily basis, I could make some progress . . .

[Mean Wing]

Also, did you have the throttle open as you checked compression? If it runs well, I wouldn't worry. Mileage indicates it's fine. I would address the things mentioned above and certainly change the belts!

Yes, sir! Per the Manual (and using the throttle friction device on the motorcycle) I had the throttle locked wide open during each test.

[wingman12]

The manual says you do not have to remove the radiator, but I found it was almost impossible to get a couple of the bolts out that hold the timing covers in place without causing damage to the radiator. You really should replace the radiator hoses anyway due to the age of your new project. Just be patient and take your time and expect it will take you several months before you can ride it. there are lots of helpful and knowledgeable people on this site that are willing and able to assist you in your restoration of a good bike. It is really to bad that work has to interfere with a persons fun. But work does pay the bills. Good luck and please keep us posted.

[Mean Wing]

You really should replace the radiator hoses anyway due to the age of your new project. Just be patient and take your time and expect it will take you several months before you can ride it.

Any recommendations for those "replacement" hoses? I've not been able to find any OEM ones.

Yep, patience is definitely a virtue, and quite advantageous in circumstances like these. Thanks!

[Maz]

Google 'Wingovations'. They are UK based although previously had connections with Randakk in the US. John, who runs Wingovations, uses this forum (Old Fogey) and is an absolute guru with these bikes. He has just started marketing some new replacement hoses for 'wings and, although I haven't bought any yet, if they're as good as the rest of his products, they will be perfect.

Maz

[Mean Wing]

Google 'Wingovations'. They are UK based although previously had connections with Randakk in the US. John, who runs Wingovations, uses this forum (Old Fogey) and is an absolute guru with these bikes.

Thanks, Maz! I'm on it!

[Aussie81Interstate]

That 17mm alternator cap nut - always gets chewed up - try some locking vice grips - or do as I did- and get a few good whacks on the edge with a cold chisel to break it loose - you might damage the cap - but you will get it off. Then make sure you grease the threads before putting it back in - and don't do it up with gorilla strength - just until it is firm.

[WINGER3]

You really should replace the radiator hoses anyway due to the age of your new project. Just be patient and take your time and expect it will take you several months before you can ride it.

Any recommendations for those "replacement" hoses? I've not been able to find any OEM ones.

Yep, patience is definitely a virtue, and quite advantageous in circumstances like these. Thanks!

When I replaced my belts on the GL1200 I also wanted to replace the rad. hoses, Honda wanted a small fortune for them so I took both hoses to Pep Boys and found 1 auto hose that would replace both rad. hoses, each end was a perfect fit and less then $12 bucks. If nothing else works give it a try, nothing to loose and could save you a lot of money. Good luck

[Mean Wing]

Good news! Though quite chewed up, the Generator Bolt Cap came loose!

Wow! I think I'll investigate that "auto" hose option. Can't see why it wouldn't do the job perfectly. I'm assuming you use both "finished" ends and cut them to the appropriate lengths?

[Ncscooter]

Napa #7733 ($16.95) does both top & bottom
Gates - #21008 does both top & bottom
AutoZone - #B70834 ($9.95) does both top & bottom
Fits 1973 to 1979 Honda Civic

Those prices are a couple years old. And yes, match the pieces you remove and cut accordingly.