Oh ***k, broke my camshaft...advice? Pics included.

rat_race

Was working on my Ninja 250, adjusting valve clearances. First time doing it. It's a shim-under-bucket engine, so need to take off the camshafts, etc., just to get at the shims.

I'm following a service manual, btw. Engine was at TDC for the second cylinder.

I took out the camchain tensioner, and then carefully took off the cam covers, as you can see in the engine pic (there is no cam cover).

Taking out the intake camshaft was fairly easy with a bit of a wiggle. However, the exhaust camshaft would not budge. I couldn't really find out why...Nothing seemed to be binding. It looked like it was slightly raised higher than it should have been on the non-chain side, but I wasn't certain (quite hard to actually see). I don't know.

Long story short is that I cranked the engine a bit to get the camchain to move the camshaft (while keeping tension on the camchain as one camshaft was already removed!), and the stuck camshaft turned. However, now it deffo was raised-up a bit on the NON camchain side...probably because there was no camchain cover keeping it down. I didn't think much of it and managed to remove it fairly easily. It didn't feel like anything took much force. But when I took the camshaft out, I noticed a crack and broke a bit off with ease (see pics). The leverage from cranking the engine must have cracked this without me even feeling it.

Now, this piece of the camshaft doesn't really do anything, it just sits into a groove. But I want to replace this camshaft for peace of mind.

Oooooops. What I think MIGHT have happened (and this is where I'd love your input), is that, when I took the camshaft cover off, maybe a valve spring pushed up and pushed the whole side of the camshaft up a bit, effectively binding the bit take broke off against its groove (which is near the camchain), making it very hard for me to take off initially.

Can I replace one of these without replacing the chain, etc?

The bike only has about 20k KM...I know normally, it's a good idea to change sprockets and chains together, but the bike simply isn't worth enough to spend so much on it.

What about buying a second hand one...bad idea?

Any input/advice/thoughts on what happened/consolation/insults welcome!

Hotblack Desiato

If I'm reading right, what happened was that you didn't release the bolts holding the top half of the camshaft bearings gradually in the right sequence. You took one end off entirely and valve spring pressure forced up the camshaft at one end while it was held at the other, which isn't great in itself...

and then you turned over the engine :eek: with one camshaft already out?!?!

and by 'cranked' do you mean on the starter?!? :eek: :eek:

Camshaft is fooked, and the bearing it sits in probably is as well, if so the head is fooked.

Also any bike I know of, you do any camshaft work with the bike at TDC on number 1 cylinder.

What exactly did the manual say about position of the engine and taking the camshaft cap bolts out?

CJhaughey

The piece that broke off is the flange that stops the camshaft from floating across the head.
You need to very carefully check the outside of the head casting where the flange sits in to make sure that that isn't damaged from the pressure of the flange snapping.
If its OK and has no cracks or damage you may have got away relatively lightly and a new camshaft will be all that's needed.
The before pic shows the chain sitting loosely on the sprockets, no apparent pressure on it, the pressure from the valve on the RHS of the head was pushing the cam upwards and binding the flange as you have already worked out.
If there is no damage to the head, a new cam and new bearing shells would be the best fix, however you will need to check all the clearances again as the new cam beds in.

rat_race

Hotblack Desiato wrote: »

If I'm reading right, what happened was that you didn't release the bolts holding the top half of the camshaft bearings gradually in the right sequence. You took one end off entirely and valve spring pressure forced up the camshaft at one end while it was held at the other, which isn't great in itself...

and then you turned over the engine :eek: with one camshaft already out?!?!

and by 'cranked' do you mean on the starter?!? :eek: :eek:

Camshaft is fooked, and the bearing it sits in probably is as well, if so the head is fooked.

Also any bike I know of, you do any camshaft work with the bike at TDC on number 1 cylinder.

What exactly did the manual say about position of the engine and taking the camshaft cap bolts out?

All cam cover bolts were were released in a gradual and sequential manner. HOWEVER, The camchain has a cover over it also, which I removed *last*, as per my f*<king aftermarket service manual (Clymer, kinda like Haynes). The official service manual (of which I don't have a hardcopy of) says to take that off *first*. So had I done that, I expect I'd not have had any problems.

It's fine to turn the crank with no camshafts as long as pressure is kept on the camchain, according to the manual. I can't see a problem with that myself as long as the timing is fixed when it all goes back in.

No, I did not turn on my ignition and attempt. I just wanted to move everything an inch or so. Are you crazy?

Both manuals say TDC on cylinder 2 for this bike.

CJhaughey wrote: »

The piece that broke off is the flange that stops the camshaft from floating across the head.
You need to very carefully check the outside of the head casting where the flange sits in to make sure that that isn't damaged from the pressure of the flange snapping.
If its OK and has no cracks or damage you may have got away relatively lightly and a new camshaft will be all that's needed.
The before pic shows the chain sitting loosely on the sprockets, no apparent pressure on it, the pressure from the valve on the RHS of the head was pushing the cam upwards and binding the flange as you have already worked out.
If there is no damage to the head, a new cam and new bearing shells would be the best fix, however you will need to check all the clearances again as the new cam beds in.

Hi CJ -- I checked and it looks ok. I think my big moment of stupidity was taking the camchain cover off last, instead of first. To be honest I just thought the camshaft covers were covers...I didn't know that they are responsible for actually keeping the camshaft pushing downwards, against the force of the valve springs: is that their main purpose? I didn't feel much resistance when taking them off, or any camshaft movement. I guess I was expecting more bolts somewhere underneath keeping the camshafts in place.

What is a bearing shell?

Wossack

not heard of shell bearings in the top end (could be wrong!), usually bottom end, attaching the rods to the crank

you should be able to drop a new cam in, just cross your fingers you've not damaged the cradles or head.. they're machined together, and not independently replaceable afaik, so be very careful with them

CJhaughey

rat_race wrote: »

Hi CJ -- I checked and it looks ok. I think my big moment of stupidity was taking the camchain cover off last, instead of first. To be honest I just thought the camshaft covers were covers...I didn't know that they are responsible for actually keeping the camshaft pushing downwards, against the force of the valve springs: is that their main purpose? I didn't feel much resistance when taking them off, or any camshaft movement. I guess I was expecting more bolts somewhere underneath keeping the camshafts in place.

What is a bearing shell?

Some cams run in a bearing shell basically a piece of metal halfmoon shaped that sits in the head and can be replaced.
Some bikes the cam just runs in the alloy head.
I don't know the Kawasaki setup but you can see if there is a separate piece of metal that the cam runs in and remove and replace if necessary.
Its going to be a pain to setup a new cam, you may need a lot of different shims to get the clearances correct.
Valve springs are strong buggers, they have to be able to control the valves at high rpms's
Best of luck with the rebuild.
Keep us posted.

rat_race

CJhaughey wrote: »

Some cams run in a bearing shell basically a piece of metal halfmoon shaped that sits in the head and can be replaced.
Some bikes the cam just runs in the alloy head.
I don't know the Kawasaki setup but you can see if there is a separate piece of metal that the cam runs in and remove and replace if necessary.
Its going to be a pain to setup a new cam, you may need a lot of different shims to get the clearances correct.
Valve springs are strong buggers, they have to be able to control the valves at high rpms's
Best of luck with the rebuild.
Keep us posted.

Thanks. I feel like a right tit. The effort just to get this far was enormous for me. The thoughts of doing all this again when the new camshaft beds in...*groan*. I could re-use the camshaft's sprocket probably, which will at least keep some of it the same.

Shims are ridiculously expensive too, aren't they?

The good news is, that all the valves were tight and out of or almost out of spec. So this process was definitely needed. Unless I screwed measuring them up too ...

I've no idea how mechanics do this in 2 or 3 hours. I had to take off the fairings, radiator, lots of hoses, tank, lots of electronics, various parts of the frame, etc. These bikes really are not designed for this. I think most people probably just run 250s in to the ground...This is a 2010 with 20k KM, so it's still valuable-ish.

But, say a 12 year old 250CC with 50k KM on the clock, a good few scratches, etc....is probably worth less than 800e. Valve clearances is hardly worth the time/effort/risk ... Especially when shims are like 30e each, and new coolant is another 15e, etc.

Opinions on this?

Wossack

you can reuse the gears off the cams, but..! if going second hand, get ones with the gears still attached, as I believe you need a special tool hold them while torquing them on without putting unwanted stress on the camshaft - going from memory though, so might be wrong about that

and as per tightness/looseness, I reckon you'd aim for going looser on the exhausts and tighter on the intakes. Writing it all out, with the desired changes to get them spot on in spec, you can often find that you can interchange the shims around to get them all reasonably good, often resulting in you only needing to buy 1 or 2 'new' shims

also, shims are cheap! 2-3e apiece. Check ebay, and search by shim diameter, rather then specific 'ninja250r 2.54mm shim etc'. Official triumph ones were like 10.50e (lol), so ebay and some searching and I found some ktm dirtbike were the same, and only cost like 2e apiece

rat_race

Wossack wrote: »

you can reuse the gears off the cams, but..! if going second hand, get ones with the gears still attached, as I believe you need a special tool hold them while torquing them on without putting unwanted stress on the camshaft - going from memory though, so might be wrong about that

and as per tightness/looseness, I reckon you'd aim for going looser on the exhausts and tighter on the intakes. Writing it all out, with the desired changes to get them spot on in spec, you can often find that you can interchange the shims around to get them all reasonably good, often resulting in you only needing to buy 1 or 2 'new' shims

also, shims are cheap! 2-3e apiece. Check ebay, and search by shim diameter, rather then specific 'ninja250r 2.54mm shim etc'. Official triumph ones were like 10.50e (lol), so ebay and some searching and I found some ktm dirtbike were the same, and only cost like 2e apiece

Thanks for the tips Wossack.

I looked at a few of the shims, most had nothing left written on them, but one said said 9 3 and another said 0 3 (the writing had started to wear though, and I thought maybe part of the 9 had disappeared making it look like a 0, but no, I think it's a 0)...meaning they're different sizes: but they measured the exact same on my vernier digital callipers (it's piece of crap, but works ok usually).

I ordered a decent-ish micrometer, which will help with the job...but from what I gathered, the shims are all the same size (2.8mm -- my calipers can't go any more accurate)

Some curious questions:

1. Wouldn't a stock bike have all the same shim sizes by default? Maybe the previous owner had the valves done but I really doubt it as there was no need for the mileage.

2. Do shims normally wear down in size with use?

milltown

The shims are used to correct variations in manufacturing to a more precise tolerance so, no, each engine from the factory will have a slightly different combination of shims.

The shims wouldn't wear down in normal use. The valves and seats will wear somewhat and the valve stems will stretch over time.

You really need a micrometer to measure the shims. If your vernier can't measure the difference between your feeler blades then it's not up to the job.

Wossack

the numbers wear if they're placed number down (so facing the valve stem). The valves naturally rotate in their seats so sort of drill the number off - pain in the ass, as you're finding, as means you need a micrometer if you want to find out whats fitted

Roadcraft

You need 7.48mm dia shims, they are available from about 1.40mm - 3.5mm thickness & go up in sizes by .05mm, they dont have to be Kawasaki shims as lots of bikes from Kawasaki, Yamaha, Suzuki, Honda & Triumph use 7.48mm dia shims.

If you go for Kawasaki parts shims will be about 10 euro each & a camshaft about 300 euro.

You will get shims for 5 euro each & there is a camshaft on ebay for 40 pounds sterling.

When you are putting it back together take your time & check & re-check your clearences a few times after turning the engine over by hand.

Best of luck with it.

rat_race

Roadcraft wrote: »

You need 7.48mm dia shims, they are available from about 1.40mm - 3.5mm thickness & go up in sizes by .05mm, they dont have to be Kawasaki shims as lots of bikes from Kawasaki, Yamaha, Suzuki, Honda & Triumph use 7.48mm dia shims.

If you go for Kawasaki parts shims will be about 10 euro each & a camshaft about 300 euro.

You will get shims for 5 euro each & there is a camshaft on ebay for 40 pounds sterling.

When you are putting it back together take your time & check & re-check your clearences a few times after turning the engine over by hand.

Best of luck with it.

Thanks RoadCraft. I actually bought that camshaft earlier, haha.

Thanks for the info on the shims...

landmarkjohn

good luck with the rebuild, rooting for ya. I've adjusted tappets but never done shims.. sounds a bit scary.. I got a VFR800 Fi that probably should be checked sometime soon.

Hotblack Desiato

Not the first time I've heard of someone led badly astray by a Clymer manual unfortunately hope you get it sorted out without too much hassle. Ebay is great. I needed a new brake caliper body last year after a thread stripped, got an entire rear brake system (caliper, hose, master cylinder) from California, in perfect condition, shipped, for about 100 euro. Place in Wales wanted £250 for a reconditioned caliper on an exchange basis, so add two sets of shipping to that price :rolleyes:

rat_race

Thanks for the responses/encouragement. Will keep you updated!

FYI, as a test, I managed to break more off the camshaft flange with a medium blow from a hammer. I'm not sure what it's made of, but it's pretty brittle.

CJhaughey

rat_race wrote: »

Thanks for the responses/encouragement. Will keep you updated!

FYI, as a test, I managed to break more off the camshaft flange with a medium blow from a hammer. I'm not sure what it's made of, but it's pretty brittle.

Camshafts are made from cast material, they are designed to be hard and resist wear, not for tensile strength.
Don't drop one on a concrete floor....

Wossack

if they're 7.48OD shims, when you work it out, pm me with what you're needing. Ive a good load of em, so might be able to do some swaps with you

rat_race

Slight progress: puts cams back in, timed it. Put cam caps and side caps back on (stressful, I found), and cam chain tensioner (resetting is annoying, but good learning experience)...glad to turn the crankshaft without hearing any weird noises.

Re-checked valves...the new second-hand camshaft, despite the 1/2 amount of mileage, has more clearance than the old one that broke. Interesting. It actually brings it closer to being within spec...still way out though :P ...

But anyway, as before, ALL my exhaust valves are way out of spec, and 3 of my intake are just at the minimum, and 1 is under. So 8 new shims for me. Was gonna buy them, but they're only sold (cheaply) in .05 increments...and I couldn't get an ideal set-up as per my recorded values. E.g. in some cases I'm too close to the min or max, and if my clearance readings are slightly out, than that .05 could bring me out of spec in some of the cases. Yes, I'm anal!

My feeler gauges (Draper) only go in .05 increments...which sucks really, so I ordered some more accurate ones (.02 or .03 increments) to hopefully get more accurate readings before buying the shims.

Wossack, looks like I'll be looking for a few shims from 2.75mm to 2.85mm. 5 x 2.8, 2 x 2.75, 1 x 2.85 is what I' be planning to buy online. Just wanna verify with better feeler gauges. If ya have any handy, lemme know...

I'll have various to give away: 2.87 x 2, 2.925 x 2, 2.9, 2.89...and might end up re-using 2.83 or 2.855.

serious3

2.95, 2.75 i really doubt that the valve clearences are 2.95mm or am i reading your post wrong? 0.12 on my ccm and 400cc yamaha quad for inlets.

Hotblack Desiato

No that's the shim thickness, not the clearance which will be a fraction of a mm.

rat_race

serious3 wrote: »

2.95, 2.75 i really doubt that the valve clearences are 2.95mm or am i reading your post wrong? 0.12 on my ccm and 400cc yamaha quad for inlets.

Yeah, I'm referring to the shim sizes...the valve clearances are all between .10mm and .18mm...

Wossack

just flying out the door, will be back later on and see what shims Ive got - theyre all in .05mm increments

and your feeler gauges should ideally going in 0.01mm increments (note you wont get a set that go 0.10,0.11,0.12 all the way though to 0.30, you'll have to make all the sizes by stacking 2 or maybe even 3 of the gauges on top of eachother to get the desired clearance)

Wossack

rat_race wrote: »

Wossack, looks like I'll be looking for a few shims from 2.75mm to 2.85mm. 5 x 2.8, 2 x 2.75, 1 x 2.85 is what I' be planning to buy online. Just wanna verify with better feeler gauges. If ya have any handy, lemme know...

I'll have various to give away: 2.87 x 2, 2.925 x 2, 2.9, 2.89...and might end up re-using 2.83 or 2.855.

checking here now; Ive only 2x 2.80, but have the others (2x 2.75 & 1x 2.85)

Doublecheck (feckin quadriple-check!) with your new feeler gauges - as its pretty heartbreaking to have waited for shims, for them still to be out when you've reassembled and checked again effectively back to square one!

Tigger

As the poem says if you can try to fix your engine
and fail but start again
With no fear or loss just carry on
Then You are a man my son

rat_race

Got the engine put back together this weekend. Bought shims from ebay. Re-check of the valves was spot on...surprised that something went my way! Did the plugs and coolant too (will do oil tomorrow and fix up the brakes as they're sticking).

Long story short is, it took a few tries before starting...but now it's running great. Turnsover/starts much quicker than it did before, and the idling when "cold" is much much better.

Kinda shocked how well it is running, seeing as I had to replace the camshaft with another second hand one, the petrol is probably a year old now, the battery was only charged a few times in the last year, and I had no idea WTF I was doing...