Jump to content

Our Official NAGF Flags

are now available in the NAGF Online Store in TWO Sizes! Don't miss your chance of being one of the first to fly the new high visibility NAGF Flag!!!

 

Click Here To Go To the NAGF Online Store!!!

 

Snag_1ffcf50.png

NAGF Admin NAGF Admin
NAGF News Ticker
     
  • Happy New Year and Welcome to 2019!!!
  • New Members are always welome!!!
  • NASR 12!!!
roscoepc

GL1200 Engine Balance - Compression

11 posts in this topic Last Reply

Recommended Posts

roscoepc

OK People I'm currently helping a Lady over at the Saunders Site with an '85 Ltd Ed cosmetically in very good shape but the engine is running like cat poopy: A dead miss caused by something.

 

Being as she's just over in Ocala I went over to take a look at the bike and found the following stuff with it. The fuel tank has been changed from a fuelie tank with the fuel return from the fuel regulator to a carb'd version without the return as near as I can tell. A return line has been "engineered" to the intake side of the fuel pump and appears to be working well.

 

When we fired her up, there was an obvious miss so I started checking and immediately noticed that the balance screw on the right rear injector was tightened down all the way. When I tried to loosen it, it actually "clicked"!! It was THAT tight!! :blink: I played with the balance/idle screws to try to get a better balance with some success but quit when I realized I was close but needed a set of manometers to really do it right!

 

She wanted to buy a set after I told her my suspicions so I told her I'd send her a link when I found her a set.. But the more I thought about it the more I got to thinking: We need to run a compression check on this Beastie just to make sure we don't have a bent/broken valve!! So when I talked to her last Wednesday I told her to hold off on the vacuum gauges and borrow a compression gauge which brings us to where we are now..

 

The compression check is as follows: 1- LR 90, 2-LF 110, 3- RR 140, 4- RF 130

 

For right now, bear with me and ignore the fact that we've got 50psi difference between the left rear and the right rear. The compression check was done by someone who hasn't done one before, BUT, and this is my observation and Question: The Left side is relatively close as is the Right side BUT the main thing I see is at least a 20lb difference between the left and right!!

 

My Question is then: Could this side to side compression difference be caused by engine imbalance??

 

One of the reasons I'm not too concerned at this point about the 90psi cylinder is this bike has sat for about 4 years I think so at this point, It needs to be balanced and run IMHO!!

 

Any Opinions, Advice Questions about this are Greatly Appreciated!!

 

And for the Record, the charging system has been "Engineered" also and is not charging at this time, But.... I think I got that part covered!!! :59fb607672645_SmileyToothSM::59fb607672645_SmileyToothSM: :roflmao:

 

 

Share this post


Link to post
Share on other sites
brianinpa

I wish I knew more about the 85 LTD models.  The fuel injection just throws me a curve, but what you are writing makes sense.   Oh, and I never worry too much about numbers from a motor until its been through a couple heat cycles.  I'd balance it, let it run for a bit, cool off, then do it all over again.

Share this post


Link to post
Share on other sites
Mountain Rider

I agree, balancing the fuel and letting her run a bit makes sense. It probably needs some run time just to get everything seated and sealed again. When they did the compression check, was there any blead off in the cylinders with lower compression, or did they hold steady?  How's the timing?  Wouldn't want to run on a bad belt. 

Share this post


Link to post
Share on other sites
roscoepc
25 minutes ago, brianinpa said:

I wish I knew more about the 85 LTD models.  The fuel injection just throws me a curve, but what you are writing makes sense.   Oh, and I never worry too much about numbers from a motor until its been through a couple heat cycles.  I'd balance it, let it run for a bit, cool off, then do it all over again.

 

Don't let the fuel injection throw you Brian. To me, the fuel injection is a lot simpler than 4 carb's!! Yeah you've got all those electronic sensors and such but that's nothing IMHO compared to the inner workings of those 4 carb's!! Besides, when you balance a Fuelie, it's only left to right side. There is no front to rear adjustment..

Share this post


Link to post
Share on other sites
roscoepc
32 minutes ago, Mountain Rider said:

I agree, balancing the fuel and letting her run a bit makes sense. It probably needs some run time just to get everything seated and sealed again. When they did the compression check, was there any blead off in the cylinders with lower compression, or did they hold steady?  How's the timing?  Wouldn't want to run on a bad belt. 

 

I didn't ask about bleed off as this was the first time they've done a compression test and I think I've got enough info to proceed. As far as the timing, she most likely needs belts but I don't think there's a problem right now as if a belt had jumped a tooth or broken, there would not be any compression in at least one of the cylinders as the 1200 is an "interference" type engine meaning the piston will nail a valve if the timing is off I believe.....

Share this post


Link to post
Share on other sites
OnaWingandaPrayer

Don , I don't know at what degrees the interference begins. If the PO had replaced belts and the cam is retarded, the valves would open/close late which could lower compression. 

What I don't understand is all this happened after a change of fuel , IIRC .

Share this post


Link to post
Share on other sites
brianinpa
(edited)
52 minutes ago, roscoepc said:

 

Don't let the fuel injection throw you Brian. To me, the fuel injection is a lot simpler than 4 carb's!! Yeah you've got all those electronic sensors and such but that's nothing IMHO compared to the inner workings of those 4 carb's!! Besides, when you balance a Fuelie, it's only left to right side. There is no front to rear adjustment..

 

Didn't you know... that why I went to a single carb

 😁

 

Also, the motor will run with a cam pulley off by 1 tooth.  You will know t hst something is wrong but it will run and not destroy itself... right away.

Edited by brianinpa
  • Like 1

Share this post


Link to post
Share on other sites
roscoepc
31 minutes ago, OnaWingandaPrayer said:

Don , I don't know at what degrees the interference begins. If the PO had replaced belts and the cam is retarded, the valves would open/close late which could lower compression. 

What I don't understand is all this happened after a change of fuel , IIRC .

 

There are a lot of unknowns on this one!! I don't think it's bad timing though as the idle/balance settings have DEFINITLY been messed with.... And Brian answered the single tooth question!!

 

But I'm still wondering if balancing will level the compression between the left and right sides somewhat......

Share this post


Link to post
Share on other sites
roscoepc

A Final Report! For right now at least!! ;)

 

Well got the gauges hooked up and Yes.. The engine was off by almost 10 inches of vacuum!!  Played with it for about 10 minutes, got her balanced right with the idle set at 1040rpm and,,,, She runs as smooth as mine!!!! ;) Now there IS some hesitation when revving the engine up but I believe that's due to the TPS being a bit "scratchy" due to the bike sitting.. I firmly believe that'll straighten itself out as the bike is run more.. Except for belts, possibly soldering the charging system wires and such, I think we're done here!!

 

BTW, I did take pic's but can't figure out how to download them from my phone to my desktop.... When I get them I'll load them!!

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites
Mountain Rider

Don, worst case with your pics, log on to the forum on your phone and down load them to the forum from there.

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites
OnaWingandaPrayer

    :thumbs-up:     Don, thanks for helping these folks out . 

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×

Important Information

By using this site, you agree to our Terms of Use,