Topic: it started life as a Test-rig

[754]

Sometimes the cam can be fixed..

[CR750]

o sorry we did not spoke to eachother......but hope you enjoyed the 'race'.

Sure, I enjoyed myself, no worries 
I went with some mates so we had a beer and watched some racing, sounds like a day out to me. 
It would have been nice to speak with you but your were in the pits area mostly when I was there ... maybe we meet in Spa or Elst ?
I met some other people like Loek, who shares another hobby ( rock climbing ) and he's building a nice bike on the MF maybe you know him ( has some problems with the injection)  EGLI TR1 ?

Anyway ...had a CB900 a few years back with a similair problem (suspected loose bolt or particle blocking oil) like your top end, but I did not notice anything while I was riding it and nobody watched me for the smoke ;-) so I ran it till it locked itself up..good scare....total top end was junk after that.... the cams looked even worse then yours, got serious hot in there...

That was also a good reminder on how important oil/lubrication in an engine is. Lacking those for a few seconds or so can easily friction weld metals together @ 10.000 rpm. It's actually quite amazing that for instance most old cars keep running after 200.000 km when their oil has not been replaced for years and years and the 'left handed' owner does not have do any maintenance on filters and such.

[voxonda]

Sound like a good day to me! I will be at Elst but not to participate, so that'll be a chance to meet up. I dont know Loek personally, but know of his very nice build on MF.

Yes, lubrication............. haven't had any issue's with it so far and this engine was rock solid for more than 3 seasons. Suspect the thread let go on that bearing cap, have a good look at that when I have removed the head.

Have to change the engine first so we can move on with the bike for a few more demo's this season, and test some more parts.

Let's keep in touch about Elst.

Regards, Rob

[voxonda]

Started to remove the head today to see if any further damage is done:


When the head was off, da........ :
The exhaust valves touched the pistons. Probable cause, loss of chain.

[Bill/BentON Racing]

Thanks for the support and comments,what cam were you running or looking for? Sad,but still kickin'.Bill

[voxonda]

Don't mention it, just wish I could be of more help for you...............Can only hope you can deal with your big loss.
I was runnin' a Web 41a since it is an F2 engine which cannot take higher lift. And even now the valves touched the pistons when chain broke.
Maybe better to look for other piston/cam combo, or even go for K-head/cylinder.

Keep the strength my friend.

Kind regards, Rob

[RAFster122s]

Voxonda, sorry you found more damage and need another motor. That is hard on the race budget.
Hope you are able to source a clean strong replacement for cheap money.
David

[voxonda]

Hey David, no new motor needed just a top-end. But already busy with it. Just no F2 head for me anymore. Going with a K head on bored cylinders with 63b cam, new valves, guides etc. And CR 31's. Will be back!

[voxonda]

Am (almost) ready to build a new head for the engine after the demo troubles we had. After thorough investigation I come to the conclusion that the main prob was in the bolt of camshaft bearing cap #2. The bolt came loose and set the destruction in progress. Now I want to avoid that same prob by changing from the 2 bolt and 2 stud arrangement to a 4 stud arrangement with 4 self locking nuts. Anyone any thought about that?

Cheers, Rob

[mec]

see my built http://forums.sohc4.net/index.php?topic=54803.25

Suggestion: go for custom made studs, M7 thread in head and M6 for the nuts. the reinforced and welded valve cover (which is from a technical Point of view crap) will be unnecessary.

mec

[voxonda]

Thanks Mec,

That is what i thought, but think you mean M8 instead of M7?

Regards, Rob

[mec]

would like to have M7.
i hate the risk of removing too much material and developing an unnecessary new oil leak.

mec

[johno]

Hi Guys,
Re the head threads......... the tip for the day is " Aluminium does not handle old age well "  under any circumstances but particularly where there is heat and pressure.    I work at an engineering company that specialises in stainless and ally fabrication, we have been making products for over 30 years and it is common for the ally to show its age such as stress cracking, flexing distortion and pressure failures etc  evan with minimal use.  it seems to start showing around the 20 year mark and thats with a middle of the range grade ally not the budget material use in the mc castings that we play with.  The issues we encounter with the head 6mm threads is not just related to a used thread problem.   You guys are good engineers so you will work out how you deal with that in a way that suits you, just dont think that the ally is good 2 mm from the existing thread cos it wont be !

Also Rob I received my head nuts today ,2 sets all present and accounted for , Thanks Mate 
Maybe we use them for the cam bolts 
Cheers Johno

[voxonda]

Thanks Johno!

Strande thing(or not) is that my problems keep coming with the, later,  F2 heads. with the K2-K6 heads never encountered these probs. And they are older.................. But def +1 on the aging of alu, rather just like ourselves. Cracks keep popping up!

Regards, Rob