Worn cam lobe

[sk1200]

Heya! Lonely Bandit 1200 rider from Montenegro here (I kid you not, there are only two mk1 1200 Bandits in the whole country). 

I have had the bike for a bit over a year, and have put 12000km on the clock since I bought it. Today, I decided it was about time to check the valve clearances, and what was supposed to be a routine procedure turned out to be a nightmare when I saw the cylinder 1 exhaust cam lobe (shown below). It has developed a sort of a lip towards the right part of it where it isnt touching the lifter. All other lobes look ok. The bike has 60000km on the clock and it runs very well - I never would have guessed it had a problem until I saw the cam.

I'd love to hear your ideas on what could have caused it and what you think the best plan of action would be (continue to ride it or do something right away)! I happen to have a spare top end, but it would be a no-no just slapping it on without finding out what the root cause is. 

Thanks in advance!

Stefan

[Buzuki]

Hi Stefan 

Probably reason for asymetric cam lobe wear is ,

-  asymetric valve clearance adjustment ,( Suzuki says that mutual valve clearance per one rocker-arm have to be adjusted in close as possible tolerance  ,and also says that valve clearance check&adjustments have to be done every 6000Km not in 12000Km period) ,

- use thicker engine oil (20W50) , since climate temperature in Montenegro is relative hot , (personally here in Serbia for decades I use ELF 20W50 semisynthetic oil mixed with 10% of STP (bluepack) oil aditive for my 88 Slingshot 750,

- any way obligatory you have to insert new exaust camshaft and four new rocker-arms , and very important : also check all four rockerarms shafts for minimum wear .

Best Regards 

 

Edited September 21, 2018 by Buzuki

[Gixer1460]

Never seen one worn like that but the second pic is showing some evidence of pitting / voids in the casting! It could be a combination of extended oil changes and/or overly tight clearances that have simply worn out the lobe. Unless Suzuki advise using different oil for your location - I wouldn't!  10w40 is usual grade and would suspect more frequent changes would be better that going heavier which maybe doesn't flow as well on start up when cold - when most of the wear occurs!

[Reinhoud]

32 minutes ago, Gixer1460 said:

Never seen one worn like that but the second pic is showing some evidence of pitting / voids in the casting! It could be a combination of extended oil changes and/or overly tight clearances that have simply worn out the lobe. Unless Suzuki advise using different oil for your location - I wouldn't!  10w40 is usual grade and would suspect more frequent changes would be better that going heavier which maybe doesn't flow as well on start up when cold - when most of the wear occurs!

You never worked on a Land Rover V8 than.

[fatblokeonbandit]

Ive got several like that in my box of scrap that ive removed from bandit engines, they normally have a worn rocker for that lobe as well, not sure which cause the problem, but looks like the hardening has failed on the follower face or the cam...

I have just replaced them and all have worked fine for many miles, the last on I did for a mate had a very slight rattle, and when  checked the tappets it was exactly like that, number 1 cyl as well...

 

Just replace the cam and the follower and she will be right, but check all the followers whist the cam is out, ive got a cam somewhere I think,,  if you cant find one, 

[Rene EFE]

10 minutes ago, fatblokeonbandit said:

Ive got several like that in my box of scrap that ive removed from bandit engines

All cil-1?

[fatblokeonbandit]

1 minute ago, Rene EFE said:

All cil-1?

When it stops pissing down ill get my fat arse  off the sofa and go outside and have a look

[Buzuki]

33 minutes ago, fatblokeonbandit said:

 but looks like the hardening has failed on the follower face or the cam...

 

 

 

 

 Suzuki cams on oil cooled engines do not have any hardened layer(cementation) , you can check that with simple file test , Suzuki just chose that type of material matching , on one side soft cams lobes surfaces matched on the other side with hard chromed surfaces on the rocker arms ,

btw,I will also check rockerarm shaft for wear since tolerance between that shaft and rockerarm directly determines amount of oil for cam lobe lubrication .

Edited September 22, 2018 by Buzuki

[Reinhoud]

I had a DR500 from 1981 for 13 years, and this (worn cam lobes and rocker) would occour when the oil level was too low, slightly too low would cause these symptoms already.

 

No idea if this could be the same with a Bandit, but may be something to look in.

[Crass]

5 hours ago, Buzuki said:

 Suzuki cams on oil cooled engines do not have any hardened layer(cementation) ,

 

Surely any camshaft lobe has to be case hardened or it would last all of five minutes?  It may well not have an added hard chromed layer but that doesn't mean it is not case hardened in some way by the metal being surface treated.

[Buzuki]

5 hours ago, Crass said:

Surely any camshaft lobe has to be case hardened or it would last all of five minutes?  It may well not have an added hard chromed layer but that doesn't mean it is not case hardened in some way by the metal being surface treated.

I do n`t claim that oil cooled engines cams are wood or plastic soft , but they are all over Relatively Very Soft surfaced compared for example with any SRAD cams or similar  cams , 

I have checked long time ago oil cooled engines several cams for surface hardness and definitely they don`t have any very hard layer surface nowhere , only what I have noticed is that when those cams are brand new packed from factory they have some very thin just few micron of black layer coating , I guess that thin black layer  is some sort of industrial graphite which helps cams  brake in procedure for first around 1000Km and nothing more .

 

Edited September 22, 2018 by Buzuki

[sk1200]

Thank you so much for all the responses, I wasn't even hoping to get so many! You guys are awesome. 

Buzuki, what baffles me is that the valves were all within spec, even those two on the offending cam. The pairs of valves were also all quite symmetric. Thanks for the advice on oil! I also noticed that when I change the oil, it seems a bit too thin for 10-40, it could be breaking down too quickly in our hot weather. I guess either thicker from now on, or more frequent changes. I'll also make sure to check the valves every 6000km.

Thanks for the offer fatbloke! I have a spare cam and rockers from a very low mileage wrecked Bandit. Pulled it out of that engine today and the lobes both look like new and measure up to spec according to the manual. I'll check the followers tomorrow, but past the visual inspection for obvious wear, I cannot seem to find any specification for it. You guys know it by any chance?

Thank you all once again! I am adding a couple pictures of my beloved bike =) 

 

[Buzuki]

Stefane 

-Since you allready have to remove and replace exaust cam for Obligatory check rocker arm shaft condition, at least for shaft for that pair of rocker arms where cam lobe was destroyed , I suspect that shaft is out of tolerance so cam lobe was less supplied with oil which caused cam lobe failure ,

- before you mounting new exaust cam is not bad praxis to polish both cam lobes and cam journals with Extremely Fine polish material on some very fine polishing wheel until cams lobes and cam journals become almost miror shine , that will extend cam life significantly , and that is my regular praxis on my GSXR750J on every 12000Km for decades ,

- chose to  insert only those rockerarms which hard chromed surface is only and only Perfect , with no any sign of wearing lines , piting holes , or any other surface deformation ,

- finally polish rocker arm hard chromed surface also ,

-  after polishing don`t forget to carefully wash with gasoline both cam and rockearms until they become perfectly clean ,

- before mounting back those engine parts use high quality thin layer of graphite grease both on cam lobes and cam journals ,

- finally change the engine oil and oil filter  with fresh ones , since is very possible that microscoping metal byproducts from cam lobe failure poluted entire engine oil system , 

- as I allready say use thicker engine oil for your very hot climate condition .

 

Pozdrav  

Edited September 22, 2018 by Buzuki

[Gixer1460]

Followers should be smooth, shiny and curved. Any ridges, flat spots, dull or scratched and i'd be replacing it as it may take out the cam. Followers are cheap compared to cams.

[sk1200]

25 minutes ago, Buzuki said:

Stefane 

-Since you allready have to remove and replace exaust cam for Obligatory check rocker arm shaft condition, at least for shaft for that pair of rocker arms where cam lobe was destroyed , I suspect that shaft is out of tolerance so cam lobe was less supplied with oil which caused cam lobe failure ,

- before you mounting new exaust cam is not bad praxis to polish both cam lobes and cam journals with Extremely Fine polish material on some very fine polishing wheel until cams lobes and cam journals become almost miror shine , that will extend cam life significantly , and that is my regular praxis on my GSXR750J on every 12000Km for decades ,

- chose to  insert only those rockerarms which hard chromed surface is only and only Perfect , with no any sign of wearing lines , piting holes , or any other surface deformation ,

- finally polish rocker arm hard chromed surface also ,

-  after polishing don`t forget to carefully wash with gasoline both cam and rockearms until they become perfectly clean ,

- before mounting back those engine parts use high quality thin layer of graphite grease both on cam lobes and cam journals ,

- finally change the engine oil and oil filter  with fresh ones , since is very possible that microscoping metal byproducts from cam lobe failure poluted entire engine oil system , 

- as I allready say use thicker engine oil for your very hot climate condition .

 

Pozdrav  

Zahvaljujem najljepse! Thank you so much for writing such a detailed description! Got it, I will do everything you said before installing. Should I just replace the rocker arm shafts with the ones from the second engine? Also, is there a better alternative to graphite grease, like assembly lube you would put on brand new journals? 

35 minutes ago, Gixer1460 said:

Followers should be smooth, shiny and curved. Any ridges, flat spots, dull or scratched and i'd be replacing it as it may take out the cam. Followers are cheap compared to cams.

The followers that I will be putting in look very smooth, so I should be good to go! Thank you!

[Buzuki]

Stefane 

Chose and instal only the best rocker arm shafts , one micrometer with 0-25mm range will be very usefull tool for measuremets od external diameter of this shafts , so chose shafts with less as possible wear and thickest ones in diameter  for instalation ,

Don`t  mix rocker arms ! , if you use cam and rocker arms from the spare second engine they have to be placed in the same order as they are placed before removing , regadless even if they are in perfect condition or is fresh polished ,

Nothing is wrong to use some original asembly lube , even quality motor oil can do the same job , worst case scenario is dry parts instalation , personally I always use  high quality standard graphite grease for that purpose .

Edited September 22, 2018 by Buzuki

[sk1200]

12 minutes ago, Buzuki said:

Stefane 

Chose and instal only the best rocker arm shafts , one micrometer with 0-25mm range will be very usefull tool for measuremets od external diameter of this shafts , so chose shafts with less as possible wear and thickest ones in diameter  for instalation ,

Don`t  mix rocker arms ! , if you use cam and rocker arms from the spare second engine they have to be placed in the same order as they are placed before removing , regadless even if they are in perfect condition or is fresh polished ,

Nothing is wrong to use some original asembly lube , even quality motor oil can do the same job , worst case scenario is dry parts instalation , personally I always use  high quality standard graphite grease for that purpose .

Awesome! Thank you so much once again for all the experience you shared, it is priceless. I will post an update when I get her running again in a couple of days

[Buzuki]

2 hours ago, sk1200 said:

Awesome! Thank you so much once again for all the experience you shared, it is priceless. I will post an update when I get her running again in a couple of days

It was my pleasure !

 But take care and take your time and don`t hurry up with that very sensitive job , double and triple check everything ,and Allways keep one eye on the original Suzuki service manual ,  all information is there , dismantling procedure recomendation , asembling procedure recomandation , recomended torque moments ,order of bolts torque , etc,...

it will be my pleasure when you anounce here that you have done repairing job succesfully , also it will be your pleasure when next time after around 6000Km you remove valve cover to check valve clearance and see that all cams and rocker arms and other parts are in perfect condition .

[sk1200]

Finally got to it today as the weather permitted! I have ran into a problem though. I have alligned intake and exhaust cam sprockets as per manual, with the correct 22 pin distance between the arrows (24 including the pins with the arrows) while the T mark on the rotor is pointing at the pickup. Before I installed the cam chain tensioner, I rotated the engine clockwise a tiny bit to remove the slack from crank sprocket to cam sprocket. Now I cannot rotate the engine at all, so either timing wrong or chain slack stuck somewhere at the bottom. 

 

Where did I go wrong? Should I remove both camshafts again and start over?

 

[Oilyspanner]

When this happens I remove the cams, the front cam chain guide and manually move the cam chain , it should come free with the front guide/blade removed. The chain bunches up sometimes and gets caught - always best not to move anything when finishing it off, everyone does at some point though !

[sk1200]

12 hours ago, Oilyspanner said:

When this happens I remove the cams, the front cam chain guide and manually move the cam chain , it should come free with the front guide/blade removed. The chain bunches up sometimes and gets caught - always best not to move anything when finishing it off, everyone does at some point though !

I did what you said and still does not turn over. Is it possible that I bent a valve or two on the first cylinder when I tightened the cam journals and something 'moved'?

[Buzuki]

Question , is the gear box positioned in Neutral position ? 

btw , if you initialy positioned cams against cranck in the right position there`s no cnance to bend valves ,

to bend valves significant force is needed .

-Regardless of your actual problem,- After cam chain timing job is done Always rotate cranckshaft several turns clockwise to be sure that valves don`t touch piston .

[sk1200]

18 minutes ago, Buzuki said:

Question , is the gear box positioned in Neutral position ? 

btw , if you initialy positioned cams against cranck in the right position there`s no cnance to bend valves ,

to bend valves significant force is needed .

-Regardless of your actual problem,- After cam chain timing job is done Always rotate cranckshaft several turns clockwise to be sure that valves don`t touch piston .

Yeah, its in neutral and the cams are seemingly in the right position, which is why I am guessing its the slack of the cam chain blocking it from turning ugh.

[Askamaskinservice]

Have you got one or more of the camshaftbearing halves on the wrong way.

I don't know how it is on a Suzuki, but i now it's no good if you put them on backwards on other engines. (so i've heard)

[sk1200]

10 minutes ago, Askamaskinservice said:

Have you got one or more of the camshaftbearing halves on the wrong way.

I don't know how it is on a Suzuki, but i now it's no good if you put them on backwards on other engines. (so i've heard)

Haha no, Suzuki have made it really easy to orient them the right way and put them in the right place =))