Figured why gs750 not starting

[BassCliff]

On the cam chain rebuild link it mentions that the parts required and their numbers are for the GS850 and that although almost all GS models share cam chain tensioner parts, to make sure they apply to my bike, an 83 GS750ES. Is there parts list somewhere on the site I can verify what I need?
thanks for any suggestions.
baz

Hi,

Go to one of the online parts fiches, like partshark.com, and order up the parts you need. I've never seen a guide for this procedure for your specific bike. Perhaps you'd like to write one?

|REF#| PART #| REQ| RETAIL| YOUR PRICE|

1 CHAIN, CAM SHAFT DRIVE (120L)
12760-45040 1 $93.31 $73.91

2 GUIDE, CAM CHAIN
12771-31301 1 $38.27 $30.88

3 GUIDE, CAM CHAIN
12782-47040 1 $106.29 $83.55

4 SCREW
02112-05127 (replaces 02112-05128) 2 $1.42 $1.18

5 TENSIONER, CAM CHAIN
12810-31301 1 $65.20 $52.42

6 CUSHION
12814-44101 2 $2.68 $2.24

7 ADJUSTER ASSY, TENSIONER
12830-33302 1 $127.74 $99.65

10 .SCREW
12838-45001 (replaces 12838-45010) 1 $5.08 $4.24

11 WASHER, SEAT DAMPER UPPER
08322-0108A (replaces 08322-11085) 1 $1.32 $1.10

12 NUT
08310-0008A (replaces 08310-11085) 1 $1.32 $1.10

13 .O RING
09280-21013 1 $1.05 $1.05

14 ..O RING
09280-06005 1 $1.05 $1.05

15 .OIL SEAL
09284-10006 1 $2.49 $2.09

16 NUT
08316-1006B (replaces 08316-16065) 1 $1.84 $1.54

17 GKT,TENSIONER A
12837-47010 (replaces 12837-47000) 1 $2.54 $2.13

18 BOLT (6X25)
09103-06212 (replaces 09128-06022) 2 $1.70 $1.42


Thank you for your indulgence,

BassCliff

 

[Big T]

First, thanks for everybody offering their advice.
So, I take off the right hand engine cover, turn the engine so the timing marks are lining up and then count the links between the cam sprockets?
How many links am I looking for?

If it did in fact jump time, does that absolutely mean it bent a valve?

thanks for all,
baz

You've missed the most important step here

Set the ignition timing marks
The arrow on the exhaust cam should point parallel to the gasket surface (this is what you missed, it times the cams to the crank)
Now, count back 20 pins to align the intake cam to the exhaust cam

Try that and see if your compression comes back. Then check the cam chain tensioner and rebuild

 

[baz666]

So align the timing marks to the 1-4 signal generator side and then look for the number 1 and the arrow on the exhaust cam? And that should be aligned to the cyl. head gasket surface? Now I count back 20 pins from the number 1 and its arrow? Am I correct so far?

Also, took out the carbs after some struggle and removed the cam chain tensioner. The pushrod spring appears very weak. I can push in the spring-loaded rod all the way in with very little effort, I mean like almost none and it pops back without much force. It's difficult to imagine the spring would have enough resistance to maintain any kind of pressure on the cam chain guide.
Other than that, the entire tensioner seems clean and the rod is not pitted or bent or anything. The knurled knob and its spring seem to work as indicated on the instructions.

One last thing, a local bike mechanic keeps insisting it's got to be bent valves. Wouldn't I feel some resistance while turning the engine by hand if it was a bent valve - and - what would bend valves in all four cylinders? I'm wondering if this guy knows what he's talking about. Sort of glad I never took a bike to him.

Any comments would be much appreciated.
thanks,
baz

 

[koolaid_kid]

If you have a bent valve the clearance would be way off due to its inability to move easily.

 

[mike_of_bbg]

The cam chain tensioner push rod spring doesn't need a whole lot of force. It will advance in the rare event that there is little enough push-back to prevent it from doing so. You should be able to push it in without too much effort - but only if you're turning the tensioner knob counter-clockwise (as assembled).

 

[baz666]

No, the rod pushes in with almost no force whether I turn the tensioner knob counterclockwise or not.

Also, since the valve clearances are all spot on, I think The Koolaid Kid makes sense when he said the valves are not bent but likely not fully closing, indicating a timing issue. I have to get the giant 30mm bolt off the back of the cam chain tensioner today to look at the internal spring - which means going to Crappy Tire (Canadian version of Sears Auto) and buy a 30mm socket. I've ordered the parts required for the rebuild. A week to 10 days I'm told. Looking at the almost warm weather is giving me added impetus.
In the meantime, since I have the carbs off and they look filthy, I'll check the float bowl height and clean out the jets, etc, give it a bath.
I have a container of Seafoam. Is that good for a carb bath?
thanks for all the help, I'd have given up without it.
baz

 

[tom203]

No, the rod pushes in with almost no force whether I turn the tensioner knob counterclockwise or not.

Also, since the valve clearances are all spot on, I think The Koolaid Kid makes sense when he said the valves are not bent but likely not fully closing, indicating a timing issue. I have to get the giant 30mm bolt off the back of the cam chain tensioner today to look at the internal spring - which means going to Crappy Tire (Canadian version of Sears Auto) and buy a 30mm socket. I've ordered the parts required for the rebuild. A week to 10 days I'm told. Looking at the almost warm weather is giving me added impetus.
In the meantime, since I have the carbs off and they look filthy, I'll check the float bowl height and clean out the jets, etc, give it a bath.
I have a container of Seafoam. Is that good for a carb bath?
thanks for all the help, I'd have given up without it.
baz

The units that I have, you could hold the 30 mm in a vice and tap adjuster body to loosen it- the knurl clears the vice jaws. As was said, you can push the rod in only when you turn knurled knob counterclockwise- release the knob and you can't push it in, but the rod can move out to take up chain slack.
You got the carbs off, you might as well give them the deluxe cleaning while you wait for your adjuster parts.

 

[Guest]

Once your done with the tensioner.

here are a few things you can try.

Since you already have the carbs off, pull all the spark plugs out and disconnect the exhaust or just move it aside.

Put a plug in # 4 and turn the engine over by hand.

When you feel the compression stroke listen to where the hissing is coming from.

At the same time look at your camshaft's . they shouldn't be pushing the valves down at all on the compression stroke.


This will tell you if its the valves,

IF your sure its its not hissing out of the intake or exhaust then open your oil cap and listen there.

If you hear it coming from there, than it narrow's it down the the rings

 

[baz666]

After disassembling the cam chain tensioner, I test-reassembled it as per the instructions from bwringer.com.
After returning the spring to the knurled knob adjuster assembly, I turned it all the way counterclockwise while holding down the pushrod and its spring, then I used the setscrew to lock the pushrod in place and setscrew bolt to secure the screw.

But, when I put the bolt on the end of the adjust assembly nut and try to tighten it with Locktite, as instructed in Step 12, I find I can turn the adjuster assembly shaft even further counterclockwise quite a ways
.
I haven't been able to get the 30mm bolt loose yet but does the above indicate there is something not functioning properly inside or is it something I'm doing wrong?
thanks for your patience,
baz

 

[Nessism]

You need to play around with adjustment on the external spring until you find the proper position. Push in the pushrod plunger, set the lock screw, and then start adjusting the external spring. You need to engage the spring with the hole in the large nut and the knurled knob, and then wind up the spring by turning the knurled knob before pushing it onto the shaft with the flats cut in it. Make sure you get nice strong spring force on the pushrod with the adjuster all the way out, and at the same time you don't want coil bind on the external spring when the pushrod is all the way in. Takes some fiddling but you will get it.

Oh, and you have it correct now about checking the cam timing: 1-4 T align, exhaust 1 mark level with the head, and then count the pins between 2-3.

 

[baz666]

While waiting for a friend to bring over a 30mm socket to open up the cam chain tensioner adjustment assembly, I had a look at the carbs. The butterflies were shut absolutely tight, not space for a hair to get between the butterflies and the carb body. So I did a bench sync and used the soft wire from a bread tie as a measuring tool. Now all butterflies are open the width of the bread tie wire when at rest. I'm thinking that having the butterflies shut tight was another reason the bike wouldn't start but I guess I rode it this way last year so who knows.
I had a look at the carb internals and no clogged jets. The floats were a little high at about 24mm. They're supposed to be at 22.4, give or take 1mm so I adjusted them. The float valves appear clean and aren't deformed in any way.
thanks,
baz

 

[Guest]

When your all done and its up and running good, Remember that float adjustment if you notice it doesn't run as good as it did last year.
There may be a lean spot or trouble idling/low speed.

 

[baz666]

One question about the carbs. There are little rubber stoppers that go on top of one of the jets. Can anyone clue me into why this is and how it works? Why are they stopped up?
thanks,
baz

 

[Big T]

One last thing, a local bike mechanic keeps insisting it's got to be bent valves.

I'm wondering if this guy knows what he's talking about. Sort of glad I never took a bike to him.

Any comments would be much appreciated.
thanks,
baz

I think you've already found the answer to that - never take your bike to him. He doesn't even understand the basics of engines. Is this the HD guy, or another one?

 

[baz666]

Yep, he's an HD guy, telling me, "Those Jap bikes are too complicated for their own good."
Uh, okay.... so much for his expertise.

Anyway, I'm beginning to figure out what happened. Ever since I got this bike, GS750ES, I've noticed some old oil gunk behind the cylinders and down on the top of the gearbox. I thought it was the two oil lines leaking. I took them off yesterday and they seem fine, pretty new actually. Then I noticed some old gunked up oil around where the tensioner attaches to the back of the engine. It wasn't until I got the entire tensioner apart that I realized it works on oil pressure. The rubber seal that locates the shaft of the adjustment assembly is pretty shot, along with the 21mm rubber seal that fits onto the threads of the big 30mm bolt. The setscrew rubber seal is also flat and kind of chewed up.
So what I'm thinking is that oil was leaking from this area, and the tensioner didn't have enough pressure to operate properly.
Am I on the right track here? Is that how the tensioner operates, off oil pressure and of course, the spring?
thanks,
baz

 

[Guest]

HD guys Saw a group of them passed by a Bergman scooter once. Not easy to look bad-a$$ in that case


The tensioner works on locking spring pressure..

It gets oil splashed on it from the cam chain throwing oil around.


That spring pushing the tensioner's plunger out is just there to push it out a bit. Not to hold the cam chain tight.


When the plunger moves out, the knob on the side rotates clockwise and actually moves into the tensioner.

Its actually moving in and pushing on the tapered end of the plunger.

that locks the plunger from moving back.

So its completely automatic


That oil you found underneath it is quite normal for aging GS's

It requires a replacement of the all the seals in the tensioner to stop it from leaking.

Hope this helps

 

[tom203]

One question about the carbs. There are little rubber stoppers that go on top of one of the jets. Can anyone clue me into why this is and how it works? Why are they stopped up?
thanks,
baz

Those plugs cover access to pilot jets- farther up column is a port that connects to main jet area to feed the pilot. These small jets clog real easy, especially after a bike sits unused and this is why folks tell you to do a thorough cleaning. When you put the fuel bowl back on the stopper is held in place.

 

[baz666]

Thanks Mechanix for the explanation about how the tensioner works and thanks Tom for the explanation about the little rubber stoppers in the carbs.

So about the tensioner, I'm guessing that since it is actually spring operated, it is critical to make sure the spring behind the knurled knob is turned at least 1 complete revolution before putting on the nut that holds the knurled knob in place. But when I rotate that spring, it seems to go off center, like it's being wound too tight.
Also, about the nut that holds on the knurled knob. How tight does it go on if the knurled knob is still supposed to move freely?
In the bwringer instructions, it says to use Loctite on that nut. So does it torque down tight enough to allow the knurled knob to turn but not to lock it in place?
Potentially dumb questions, I know, but any help at all is much appreciated.
thanks,
baz

 

[Big T]

Thanks Mechanix for the explanation about how the tensioner works and thanks Tom for the explanation about the little rubber stoppers in the carbs.

So about the tensioner, I'm guessing that since it is actually spring operated, it is critical to make sure the spring behind the knurled knob is turned at least 1 complete revolution before putting on the nut that holds the knurled knob in place. But when I rotate that spring, it seems to go off center, like it's being wound too tight.
Also, about the nut that holds on the knurled knob. How tight does it go on if the knurled knob is still supposed to move freely?
In the bwringer instructions, it says to use Loctite on that nut. So does it torque down tight enough to allow the knurled knob to turn but not to lock it in place?
Potentially dumb questions, I know, but any help at all is much appreciated.
thanks,
baz

Just make it snug - the Locktite will hold it in place. You don't want to overtighten and snap it off.

 

[mike_of_bbg]

I don't think one turn of tension on the spring is enough. I'm thinking 2, maybe 2-1/2. If it's too loose it's going to rattle.