StromTrooper banner

This Sucks , Loud noise in front cylinder

4K views 23 replies 12 participants last post by  teevee 
#1 ·
I was heading home from a ride this morning, and about 7 miles from home I thought the engine sounded a little different, but wasn't sure, but when I got back to the house and got my helmet off, I knew something wasn't right.

Looks like I'm the third victim to go through the broken cam gear after adjusting the valves.
Not sure why this happens, as I know I'm very careful and meticulous when working. I noticed where it broke was right where the spring sets in the gear, the thinnest part of the gear.
I did the first valve adjustment on my 05 Vee about a 150 miles ago, it just turned about 18K miles, posted a youtube video of it.
Anyway, it's time to find the missing pieces, or rebuild the motor.:furious:
 

Attachments

See less See more
1
#3 ·
I have no idea! The way the gear is sitting in the picture is the way it was when I installed it, after the valve adjustment. So there was no way that torqueing the cam journals put any pressure on that part of the gear.
Crazy stuff!!
 
#4 ·
Some engines are never the same once they,ve been "opened"
All the SV engines I,ve heard of being checked for valve clearance havn,t needed any shim ;)
general concensus with the SV engines is "just leave them alone" untill 80,000 kms, then "have a look" (only if you're fussy!)
 
#13 ·
Every DL motor I've checked or my friends have checked the valves have needed shim adjustments at the first or 2nd interval.

No way I'd neglect to check/adjust them.

Risk of what happened to the OP is exceedingly rare.
 
#8 ·
Well I hit the jackpot and found all the pieces. They were in the bottom of the oil sump, under the filter, that's located below and behind the clutch basket. Boy did I get lucky or what!
Just went on ebay and found a set of cams for 75$, looks like I may be back and running by next weekend.
 

Attachments

#9 ·
These bikes with shim under/over fish bucket stuff is why I let an experienced mechanic check my valves or personally ignore them myself.
I loved my old Honda and Ariel. Undo a little round cap and use a wrench and screwdriver to set the valves. No yanking cams and other irksome efforts.
Complicated mechanicals don't make the sun shine brighter on my riding life.
 
#10 · (Edited)
Cam directly on shim and bucket valve trains are significantly lighter than rockers allowing higher rpm and horsepower running. They also need adjustment less than bolt and locknut adjusters. The scissor gears on the camshaft allow quieter valve trains than straight cut gears and less expense and complexity than double helical gears while still allowing easier cam removal than the cam chain over camshaft sprocket drive on 650s. There are trade offs everywhere.
 
#15 ·
There was no extra step ignored, it was just a weird thing that just happened. I have adjusted valves on literally 100s of bikes and have never had a problem, just unlucky this time. But I am glad it was my bike and not someone else's.
 
#16 ·
The first check is the most important one. You find out how well the factory did the job on that check. After that, figure any changes are pretty slow. 1000s change faster than 650s and exhausts change faster than intakes. I had one exhaust clearance move one leaf on the gauge tighter in 33,000 miles on a Wee while the rest were unchanged. I don't have any personal experience on a 1000 but the larger valves are a bigger hammer on the heads. Once broken in, out engines pretty much only tighten clearances. The valves pounding into the heads cause more change than cam lobe and tappet wear. Changing shims is easier on a 1000 because the cams come out without derailing the cam chains. Here's a poll on the subject. A big limitation on the poll numbers is the relatively small number of bikes that went far enough for multiple valve checks.

http://www.stromtrooper.com/informa...stment-poll-those-who-have-done-had-done.html
 
#17 · (Edited)
Agree. On shim under bucket engines valve train wear is minuscule over (more than) the life of the rest of the engine. The biggest wear area there is valve face to valve seat where the valves are hammering relentlessly during running, and that causes the clearances to shrink. The exhausts tend to be somewhat protected by exhaust carbon deposits, which result in the intakes being most vulnerable to getting too small, though this obviously depends on the specific engine design and materials chosen for valves and faces.

Many DIY home wrenches will adjust valves when they don't really need to be, which is an increased risk of "something going wrong". If the clearance is "in spec" it's in spec. Leave it the heck alone. Lot of people think if it's close to the limit they should just tweak it in, cause it will run better. It won't, and you are only adding to your risk of potential "bad things". In reality, the engine will run its absolute best when the clearances are the least, right up until it is too tight and your valves can't close and you burn a valve.

Even the best of us have these bad things happen, so don't beat yourself up over it. But knowing when you can safely reduce that risk is a really good thing. So, don't adjust valves that are ni spec. (not saying that you did)

It would be of interest to know what the actual mechanism is that stresses that thinner part of that cam gear, which results in the crack and failure, so that others could avoid duplication. I would suspect that it happens during the cam replacement process... maybe due to the torque of the valve springs against the cam while re-tightening the camshaft bearing caps, but that is just a wild ass guess.
 
#18 ·
I also wonder if an adjuster may inadvertently force the mating gear tooth into the small offset between the teeth of the scissor gear rather than the large one, putting pressure on more than just the springs.
 
#19 ·
I remember working on a bike many years ago, can't remember make or model, but it had a scissor gear. But it had a hole through both gears to align the teeth before you installed the cam, which makes more sense to me, not putting pressure on the teeth to install it. That being said, the part that broke was not the part of the gear that was getting the pressure put on it.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top