GS550 Engine rattle

[bill_face]

I was on my way back home yesterday when my '79 GS550 started making a funny rattly noise. I stopped and had a little look, and it seemed to be coming from the engine. As I was late and about 20miles from home I decided to press on.

The rattle was worse at low rev's and it seemed to go away at higher revs.

I got home, and this afternoon took it up to my local garage for their opinion. The man there never seems pleased to see me or my aged Suzuki, but he came and had a look/listen. He said the noise was possibly the timing chain was loose or the tensioner was broken. However they are always busy, and the next time he could look at it was in 3 weeks. He said not to ride it, apart from cautiously back home.

On the way home it cut out and wouldn't start again. When it cut out it was making a more low pitched noise than normally and would do the same when i turned it over trying to restart it.

I've taken the top off the engine the timing belt looks fine (i'll attach a photo).

The mechanic is not keen on looking at it, as he thinks it'll be expensive and for some reason thinks I'm not rich. He was suggesting aiming for an engine swap instead.

I was thinking I would have a go at investigating further myself, hopefully with some pointers on here about likely culprits.

So if anyone has any ideas do let me know.

Cheers

 

[Guest]

Has your chain jumped a tooth? Cam lobes look to be a little out of position.

I would suggest taking the tensioner out, and checking the operation. Then making sure your timing is ok.

Might as well check valve clearances while you're in there.

 

[tom203]

Yes, sounds like tensioner lost contact.. Look for the numbers on both camshafts like this pic
Mark #1 on exhaust camshaft shoukd be horizontal pointing forward. #3 on intake will be a certain number of chain pins fom #2 mark. Also look at camshaft ends - note the two slots facing each other when #1 mark is correct.

 

[bill_face]

Thanks for the input.

I'll have a look in more detail tomorrow, but it does look like the camshaft alignment is out. This is my first time inside the engine, so excuse the possibly stupid questions:

How do you go about manipulating the alignment? I'm guessing you slacken off the chain so its not making contact with one of the camshafts and then twist that somehow.
Could I get all of this done with the engine still in the frame? I'm presuming I'll have to remove the carbs though...

 

[tom203]

First thing is to get camchain tensioner out and inspect...it might be froze up or just installed wrong at some point (so it could not automatically take up chain lack). You might be able to get at it without carb removal, i don't know. Repostioning the chain to correct marks ain't hard, but you need the factory service manual.. I can't find it now, but hopefully someone else will chime in!

 

[Steve]

Yes, verify that the timing marks line up (or not). If you do need to adjust the timing, you will need to remove the ignition cover off the right end of the crank. Note that the RIGHT end is referenced as if you are sitting on the bike, ready to ride. The right end of the engine is under your throttle hand. You already have the cylinder head cover off. You will need to remove the cam chain tensioner, but you will also have to remove the carbs to be able to do that.

It's all outlined in the manual, but you start by setting the crank on the 1-4 T mark (right end of crank), then make sure the #1 arrow on the exhaust cam is pointing to the edge of the head. When it is, you will find #2 arrow pointing UP. Count the number of pins specified in the manual to the #3 arrow on the intake cam. Note that when you count, the pin that is directly over the #2 arrow is your #1 pin. Do NOT use it as a zero reference point and start with the pin next to it. Same thing at the other end. Whatever is specified (I don't remember if yours is 19, 20 or 21) will be directly over the #3 arrow.

.

 

[gustovh]

Do not forget to turn the engine over by the big nut.

V

 

[bill_face]

Hello again.

So I've had the bike apart today, and found that the chain was 6 places out of alignment. It should be 20 between points 2 & 3 but it was 26.

Here is a link to me turning the engine over at this point and there was a bit of a jumpy thing going on:

https://www.youtube.com/watch?v=Im2mSdq9ZSw

So I got the cam chain tensioner out and that seemed to have seized up. I've freed it up now and it seems okay. The bike had spent 5 years or so off the road, and brakes and clutch cable had seized up so I can add the cam chain tensioner to the list.

I then had a go at checking the valve clearances. They were close to or within spec (out of spec ones were too tight), but it was hard to get a reading with intake valves with the cam-shaft ellipses in the correct position because as you wind the engine round they jump at a certain point and always jumped past the point i wanted them to be at.

So I took off the intake camshaft to get it aligned thinking this would help me get a better reading.

However, the valves are now stopping camshaft from sitting down properly.

So I'm wondering if the valves are moved by the force of the ellipses pushing them in? Should I just crank that camshaft down and force them in?

 

[tom203]

6 pins out? You're scaring me. Anyway, put the intake cam back on aligned as close as you can..the cam lobes will fight you, but for now get it close. I'm worried that valves kissed pistons.

read this other thread from beginning. Get the crankshaft on "T" mark .

https://www.thegsresources.com/_for...-Adjustment-(find-TDC)-on-8-valve-1979-GS850G

 

[hampshirehog]

Very likely you've bent a valve or 2. It'll show up when you check the valve clearances if you have. Give me a shout if you need some - I'm pretty sure I've got some in the garage.

 

[bill_face]

I've got the camshaft back on, and measured the valve clearances. They were as follows:

Exhaust

A >>0.03mm >.0.05mm B >0.3mm >0.05mm

Intake

C >0.03mm >>0.03mm D >0.1mm >>0.03mm

>0.05 means I could get the 0.05 feeler gauge in, but it was a bit snug and didn't go in or out cleanly. the size below would have been smooth. As 0.03 was the smallest size I had >>0.03mm means i couldn't get that gauge in. I also didn't have any gauges between 0.07 & 0.1

So according to the manual possibly only one of them are in spec, but quite a few of them are close.

I then may have got ahead of myself I thought it would be a good idea to do a compression test. However I didn't put the cam chain tensioner (as the chain had been moving round alright when i was lining it up), or the cam cover back on (i destroyed the gasket getting it out, and didn't think it was necessary to get a compression test result).

I tested two of the plug holes 3 & 4, by cranking with the kick starter and found no compression. Then I started wondering if my compression gauge was working, or that i was doing it right? Then I went back to try again and the engine had seized. I couldn't push the kick starter or move it at the timing nut. I'm guessing that the chain has maybe jumped down in the bottom somewhere and cocked stuff up.

Any ideas on a way forward kind people?

Many thanks

 

[Guest]

Use the nut by the points plate to gently rock the pistons back and forth (as in very small movements, and without any great pressure), while pulling the top of the chain gently upward. It will be jammed down by the crankshaft sprocket.

 

[bill_face]

The rocking it a bit method freed it up a bit, but it only seems to go half a turn forward and then it has to go backwards to go forwards again...Argghh

I made a little video here: https://www.youtube.com/watch?v=T7wLcN4CW8c&t=3s

 

[leftlostcommonsense]

An engine swap may be your best bet unless you have the time to research, research, and do some more research before doing anything else. I could be wrong but from what I've seen you're lost and have possibly caused more damage or alot more work needing to be done by tinkering...couple hundred bucks'll get you another engine and you'll have spare parts from the old engine or you could pay a couple hundred bucks probably more to have someone else do all that's needed to fix this one. You could go about doing it yourself but I feel (just my opinion) you need to be doing alot more reading instead of tinkering as of right now. At the very least you're looking at having to pull the head and fix valves along with reassembling/timing everything...I wish you luck my friend, hopefully you get it going again instead of leaving it to rot like so many others do.

 

[bill_face]

Thanks for the input. I am considering an engine swap but at present I have only found a later engine to swap and not the carbs, exhaust & airbox to go with it. I've tried all the breakers within 100 miles of Bristol.

Does anyone have a spare engine???

In the meantime I'm going to continue tinkering as I'm quite enjoying learning about all this stuff. I have found a video series by Urban Monk where a chap in LA rebuilds the same engine: https://www.youtube.com/channel/UCWKqIhu2ZsdUyfNPGsK8vzw/playlists

So I'm going to follow that along, but I was kind of hoping I might be able to get a quicker fix, with help along the way on here.

You are right that I am currently lost though : (

Anyone got any more ideas why my engine won't go forward? : https://www.youtube.com/watch?v=T7wLcN4CW8c&t=3s

 

[Guest]

I expect the chain jammed going forward, so you need to release it by going backward. Try doing the same as in the video, but with the emphasis on going backward, and pulling upward on the chain with your other hand. Wrap a rag or something round the chain so you can get good purchase. You probably have a couple of links folded together and jammed in the bottom of the chain tunnel. Don't be afraid to give it a good pull.