Author Topic: 75k kms, is the cam chain still safe  (Read 205 times)

Offline user11235813

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75k kms, is the cam chain still safe
« on: July 31, 2020, 01:15:10 AM »
OK, I've just had a look around the forum and I'm shocked to discover that the engine has to be split to install a new cam chain, so it's not a job I would do. However I am wondering how safe it would be to leave it.

The CCT looked pretty good when I last checked it to put new gaskets on it, and last time I had the valve cover off the chain seemed good. There's no obvious noise. I'll be checking the valves again in a day or two so I can measure the links across the top. But if it's out of spec but it all seems good should I be worried.

I do not fang the bike much, mostly riding around at between 4 and 6k rpm. Consequently the bike does not use much oil, 300ml per 6000k kms. And there are no leaks anywhere, so I guess as far as cam chains go it's not had a hard life.

If it does start to go will I get some warning. Do cam chain spontaneously break or do they just stretch and then it becomes obvious that it needs to be looked at.

How long can an OEM CT last on a bike ridden fairly gently?

thx.

Offline The Buddha

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Re: 75k kms, is the cam chain still safe
« Reply #1 on: July 31, 2020, 03:30:19 AM »
Cam chain can last several 100's of 1000's of miles. The catastrophic failures of those are due to - you guessed it, CCT or that rear guide - which also needs cases split to install.
Now someone has to have experimented with a master link style chain - its the same as a bicycle chain isn't it.
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Offline user11235813

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Re: 75k kms, is the cam chain still safe
« Reply #2 on: July 31, 2020, 06:57:02 PM »
OK that sounds reassuring. I'll check back in a couple of days when I have the measurements on the came chain pins. The service limit is apparently 158mm across 21 pins counting the first pin as 1 and the last pin as 21. I did a rough check a fair while ago and it seemed pretty close to that. I'll do a more accurate measure this time, but for the moment assume that it's on or even just outside the 158mm limit where they say to replace the chain, if it all seems good i.e. no noise, can that safely be ignored? When winding the motor by hand to set the valves, is there anything that I should watch for regarding the cam chain?

For example Suzuki say to replace the OEM fuel line after 4 years but that is overly pessimistic.

thx

Offline The Buddha

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Re: 75k kms, is the cam chain still safe
« Reply #3 on: August 01, 2020, 05:40:26 AM »
When you are cranking the motor by hand look between the cam sprokets and if the chain ever sags inbetween, then the CCT should be replaced. Else replacing a cam chain on this bike is only when splitting the cases (as in never).
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Offline Joolstacho

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Re: 75k kms, is the cam chain still safe
« Reply #4 on: August 01, 2020, 04:58:30 PM »
No crankcase splitting is necessary. You can get access from the cam cover, and with care, replace the chain from there. You'll need to re-rivet the chain.
I've done it, and my qualified m/c mechanic has been doing it for something over 30 years with no problems.
If I were you I'd put a new camchain tensioner on it though, -cheap insurance against possible (expensive) tangling of valves and pistons.
With the camcover off you can measure the distance between a certain number of links which will tell you how worn the chain is.
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Offline user11235813

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Re: 75k kms, is the cam chain still safe
« Reply #5 on: August 02, 2020, 01:39:56 AM »
Checked it today, and it turns out to be 155mm 3mm inside the wear limit. Chain is nice and tight across the top, cam guides look good as far as I can tell so it's all ticketty boo then.

Finally pulled out the front valve shims today, swapped the front two over one was a 262 and the other was a 268, didn't really work out so I swapped them back. It seems that after popping the shims out and snapping the valves closed a few times when the valve tool slips, appears to have given me slightly different readings. Some time ago they were getting bigger spacing which I thought was carbon build up, but they seems to have settled down now and the left one has tightened up a bit. Maybe I shook some carbon build up off.

 I thought the shims only came in units of 005?, maybe it's because they use more fine grain one at the factory?

« Last Edit: August 03, 2020, 01:22:45 AM by user11235813 »

Offline user11235813

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Re: 75k kms, is the cam chain still safe
« Reply #6 on: August 02, 2020, 05:23:44 AM »
Oh noes, I put the shims in upside down so the numbers are facing up, is this going to be a big deal or can it wait a little while, as I'm going to install a new shim anyway in a couple of weeks.?

Offline The Buddha

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Re: 75k kms, is the cam chain still safe
« Reply #7 on: August 02, 2020, 07:44:10 AM »
Factory shims are all possible numbers - 261, 262, 263 etc etc.
These shims also wear a little - they are harder than the cams so much of the wear is cams and valve seats (due to heat) but I've seen a 250 shim measure 248 etc.
Number up - could get worn out, but it doesn't hurt otherwise, IMHO number is just a starting point anyway.
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Offline user11235813

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Re: 75k kms, is the cam chain still safe
« Reply #8 on: August 03, 2020, 01:41:09 AM »
Right exhaust is currently .09 with a 262 shim
Left exhaust is  currently .05 with a 268 shim

I tried swapping them around thinking that I could get the left to .13, which it did, but the right one was too tight at .03 for me while waiting  for a new shim

However seeing as I can only get a 260 or 265 for the left, I can only increase it .02 or .07 so I'd really want something in between to match the valve gap.

So I'm thinking now would be a good time to increase both exhausts to .13 which I've heard doesn't do it any harm. Do you think it's worth putting the 262 on the left to bring that up to .13 and purchasing a 265 for the right to bring that up to .12 or should I leave the right as it is at .09 and get a 260 for the left to bring it to .07 or even .12.

« Last Edit: August 03, 2020, 01:42:34 AM by user11235813 »

Offline The Buddha

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Re: 75k kms, is the cam chain still safe
« Reply #9 on: August 03, 2020, 07:30:56 AM »
Measure all your shims - I'll bet some of em are worn a little. Write the new number on them and viola, new shims in all sizes.
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Offline Bluesmudge

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Re: 75k kms, is the cam chain still safe
« Reply #10 on: August 03, 2020, 09:37:14 AM »
Your clearances are right in spec so I wouldn't do anything. If you really wanted to mess with them, leave the 262 on the right for .09 and put 265 in the left for .07. That would be slightly better.

"So I'm thinking now would be a good time to increase both exhausts to .13 which I've heard doesn't do it any harm."
-Well, I'm not convinced that it doesn't do any harm. I had to replace 2 exhaust valves at 42,000 miles due to badly worn valve seats after 20,000+ miles of running at the wider exhaust valve spec. My hypothesis is that the greater clearance causes greater force applied to the valve seat and thus accelerated wear. Not having to change shims does not equal 0 wear. It just means the two surfaces are wearing at similar rates.

I think I'm going to go back to Suzuki spec. Aiming for .08 instead of .13

If you leave the shim in upside down the cam will wear the numbers off the face.
I have yet to see a shim "wear" as The Buddha describes. But he does have a lot more experience than me. My shims have always read the stated size when I measure them with digital calipers.
« Last Edit: August 03, 2020, 09:40:32 AM by Bluesmudge »

Offline user11235813

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Re: 75k kms, is the cam chain still safe
« Reply #11 on: August 03, 2020, 05:53:54 PM »
@smudge,

Yeah, I'm tending to agree with you, I've ordered a 265 from suzuki, only $20 AUD, I thought it was going to be more. I guess it's the old question of do the suzuki engineers who built the bike know what they are doing. Prolly. I mean I've already done 75,000 and both inlets have remained steady on .05mm to .06 and the front right started on .09mm when out to .11mm then back to .09 and the front left started at .08mm and has only gotten to .05 after 50,000 kms, so that seems pretty good. I'll take it back out to .07 next service and I'm golden.


Offline The Buddha

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Re: 75k kms, is the cam chain still safe
« Reply #12 on: August 04, 2020, 11:15:13 AM »
Make sure the shims are not those cast K&L crap we got a few yrs ago.

Also you need to measure the shims with a micrometer especially where you see a wear pattern, a vernier even an accurate digital one would just bridge those grooves.

Wider clearance means less wear on the seat and valve, valves radiate heat by contacting the head, the longer they sit touching the head, the less heat they carry on average and less wear as a result. You may have just been a "beneficiary" of that legendary suzuki of spain quality. Or more than likely bad luck or weather there vs here or use type or flavor of oil or something else. 42K is no joke in any case. FWIW, I ran close to the tight end of the clearance most of the time, used 50 and 60 wt oil for a long time, ran synthetic car oil before I had excessive use, and ran 10w40 accel for the last 5-6K cos it was like 60c a quart vs the valvoline's $3 and unobtanium status. But who knows what made a difference. Mine were all between 250 and 275 all the way across.

And bloody hell $20 for a shim ? There was a shop in australia I emailed ~10-12 yrs ago that would make them etc etc but then again 300-500 for a 100+ shims wont really be cheap would it.

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Offline Bluesmudge

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Re: 75k kms, is the cam chain still safe
« Reply #13 on: August 04, 2020, 07:43:20 PM »

And bloody hell $20 for a shim ? There was a shop in australia I emailed ~10-12 yrs ago that would make them etc etc but then again 300-500 for a 100+ shims wont really be cheap would it.


Thats probably $20 AUD. I think New OEM Suzuki shims are $14 US here so that sounds about right for them upside down Australia dollars.

Offline user11235813

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Re: 75k kms, is the cam chain still safe
« Reply #14 on: August 05, 2020, 11:32:32 PM »
Yep $20 AUD is about $14 USD. I don't know if it's because I don't really go into the high revs much but the shims look pretty new, I can easily see the machining on them. I'm just going to have to trust the measurements because to purchase a good quality micrometer that will give me an accurate reading down to a ten thousandth of an inch is more than I want to spend. Particularly as I have it up for sale anyway.

I'm not ashamed to say that in the end I've rejected the Speed Twin because I fell in love with a 2013 Guzzi V7 Stone with Agostini pipes which bring out the low down growl. I'll know on Saturday if it's gonna happen. it's the right price for my limited budget, but having owned a Boxer in the past, the big rounded pots sticking out the side is very appealing to me. This is the one I'm hoping, but there are three others in front of me with first refusal. https://www.bikesales.com.au/bikes/moto-guzzi/v7-stone/new-south-wales/
« Last Edit: August 05, 2020, 11:34:57 PM by user11235813 »

Offline peteGS

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Re: 75k kms, is the cam chain still safe
« Reply #15 on: August 06, 2020, 02:22:40 AM »
Sorry I hadn't seen this thread... if you want good economically priced shims down under go here http://www.precisionshims.com.au/

Haven't bought any for a couple of years but they've always been something like $9.90 each and they express post. Good quality shims, I'm not the only one who uses them and they've served well so far.
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Offline user11235813

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Re: 75k kms, is the cam chain still safe
« Reply #16 on: August 06, 2020, 04:47:01 AM »
bejeezus, it's like shim heaven. I think I'm gonna be OK with the one I already ordered, but I see they do incremental sizes so I'll order a 358 as that might be better, excellent. There's another thread where this is exactly what they need a 29.5 that's thinner than what suzuki can supply. I'll post the link there.

http://gstwins.com/gsboard/index.php/topic,73252.20.html

« Last Edit: August 06, 2020, 05:08:03 AM by user11235813 »

Offline The Buddha

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Re: 75k kms, is the cam chain still safe
« Reply #17 on: August 06, 2020, 06:22:12 AM »
We should put a US kit together I think.
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Offline peteGS

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Re: 75k kms, is the cam chain still safe
« Reply #18 on: August 06, 2020, 03:22:52 PM »
Just remember there is a minimum shim thickness and you shouldn't go below that. If you need to go too thin, something else is seriously wrong with the seat or valve, and you're likely to end up with the cam lobe hitting the lip around the edge of the shim bucket also.
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Offline user11235813

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Re: 75k kms, is the cam chain still safe
« Reply #19 on: August 06, 2020, 05:22:55 PM »
I've just gone back through my log book and I've just been relying on my incorrect memories as to what the exhausts were reading. over the last 60k the inlets have pretty well stayed constant at .06

I remember when both exhausts gradually increased their clearance from 05 to 06 then to 09 and I panicked a bit about that because around the same time weird stuff was happening which later turned out to be the a press fit part in the carburettor coming loose which I fixed by putting a new set of carbs in.

I probably got overly worried about what was causing the increase, in clearance, was it carbon build up? Who knows. But looking back through my logs it looks to be not as bad as I remembered. I did put a half dozen tanks of this liquid moly petrol additive through my engine https://www.supercheapauto.com.au/p/liqui-moly-liqui-moly-carburetor-and-valve-cleaner-300ml/156710.html

Whether that did anything or not i don't know but the left exhaust dropped back down to 06 but 20k kms later it's still only at 05 so that seems pretty good, but the right has stayed at it's larger .09 but but not been getting worse so maybe I just got a little overly worried. However if nothing else I suppose this shows that the GS seems to be happy with standard clearances but then I stay pretty easy on the revs. I'm just gonna take the left exhaust up to 08 to match the right and call it call it done.

25k   intake  L+R  .06       exhaust L+R .05

35k   intake L+R.06         exhaust L+R .06

45k intake L+R .06          exhaust L .08   R .09

51k intake L+R .05/.06         exhaust L .06   R .09

75k intake L .05  R .06   exhaust left .05 right .09

 

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