Exhaust Camshaft problem

Message

Taqman · #1 Post by **Taqman** » Sun Mar 04, 2012 4:51 pm

OK starter for 10....

What's wrong with this pic - its the rear cylinder head at TDC

Answer - the exhaust cam is pointing the wrong way!!! the right hand camshaft should be pointng to the right not left!

I think this is what they call a 'spun camshaft'
Basically I've been trying to get my old falco running again after standing for nearly a year.

It had been very reluctant to fire but finally did and roared off to the revlimiter then stalled - since then trying to get it to run has been nearly impossible with massive blowback through the rear throttle body.

I knew something was wrong - but didn't expect this!

New/replacement camshaft will be required me thinks

Anyone got one?? and does anyone know are the front and rear cams interchangeable?

Cheers

Taq

D-Rider · #2 Post by **D-Rider** » Sun Mar 04, 2012 5:25 pm

As I said on AF1 - yes, immediately spotted the problem.
I just hope it hasn't led to a piston-valve interface moment .... but fear it may have .....

fatboy · #3 Post by **fatboy** » Sun Mar 04, 2012 8:34 pm

I have never delved into a Falco lump, Ive never flicked thru a Falco manual ( cos they dont exist ) so I dont know if its belt or chain but Id say there is a major timing issue going on there. If the cam is damaged it it would probably be in 2 pieces (snapping under the strain of pushing a valve thru a piston crown ). Looks like a tensioner/drive train failure
Many more people know much more than I
Griff @ aprilia performance is worth a call 01827 285500

Taqman · #4 Post by **Taqman** » Sun Mar 04, 2012 9:09 pm

I'd hoped so too,

Unfortunately the cogs dont lie....

Timing marks line up - camshaft in wrong position.....

taq

anzacinexile · #5 Post by **anzacinexile** » Mon Mar 05, 2012 9:19 am

Ouch

Aladinsaneuk · #6 Post by **Aladinsaneuk** » Mon Mar 05, 2012 10:22 am

the falco (workshop) manual that does not exist can be found at http://www.martinpoll.dk/div_april.htm

(There is a separate section to our forum called links, with its own aprilia section)

I have also added a sticky to the aprilia technical section with the link to help others find it in the future

D-Rider · #7 Post by **D-Rider** » Mon Mar 05, 2012 5:05 pm

Aladinsaneuk wrote:the falco (workshop) manual that does not exist can be found at http://www.martinpoll.dk/div_april.htm

There are still people that don't know? ..... we must post links to it about once per fortnight

Aladinsaneuk wrote: I have also added a sticky to the aprilia technical section with the link to help others find it in the future

..... and was already in a "sticky" ..... this one: https://www.ridersite.com/viewtopic.php?t=3255

Aladinsaneuk · #8 Post by **Aladinsaneuk** » Mon Mar 05, 2012 6:18 pm

I only had a quick look

Perhaps I should have used search?

fatboy · #9 Post by **fatboy** » Mon Mar 05, 2012 7:30 pm

Thanks Aladin, yes there are still a few dimwits out there (like me )

irich · #10 Post by **irich** » Wed Mar 07, 2012 8:54 am

How do you get a cam 180 degrees out if the timing marks line up? Has the cam shaft moved relative to the cam pulley? (I notice that there seems to be 3 allen bolts missing from the left hand pulley)

Taqman · #11 Post by **Taqman** » Wed Mar 07, 2012 1:48 pm

irich wrote:How do you get a cam 180 degrees out if the timing marks line up? Has the cam shaft moved relative to the cam pulley? (I notice that there seems to be 3 allen bolts missing from the left hand pulley)

As far as I can guess - the exhaust valves must have been siezed

When I tried to start it the cam tried to open them but met too much resistance so the shaft twisted around within the collar where the camsfaft gears attach (the shaft is a pressed fit into the collar) The bolts are out because I removed them - but the cam is in the position I found it - the mounting holes are positioned just so that the gear can only fit in one position

This is a 'spun camshaft' - not unheard of with these motors but very rare at the same time.

Taq

irich · #12 Post by **irich** » Sat Mar 10, 2012 6:24 am

Taqman wrote:
irich wrote:How do you get a cam 180 degrees out if the timing marks line up? Has the cam shaft moved relative to the cam pulley? (I notice that there seems to be 3 allen bolts missing from the left hand pulley)
As far as I can guess - the exhaust valves must have been siezed

When I tried to start it the cam tried to open them but met too much resistance so the shaft twisted around within the collar where the camsfaft gears attach (the shaft is a pressed fit into the collar) The bolts are out because I removed them - but the cam is in the position I found it - the mounting holes are positioned just so that the gear can only fit in one position

This is a 'spun camshaft' - not unheard of with these motors but very rare at the same time.

Taq

Bad news and sorry to hear it. I've never heard of a seized valve before. I'm suprised they don't key or spline the cam pulley to the camshaft.

Aladinsaneuk · #13 Post by **Aladinsaneuk** » Sat Mar 10, 2012 6:37 am

I believe they did on later variants of the engine

Taqman · #14 Post by **Taqman** » Sat Mar 10, 2012 10:14 am

Aladinsaneuk wrote:I believe they did on later variants of the engine

Later models have a forged single piece camshaft so this cant happen.

Anyway - saga continues....

Ok so I got a leaktester

Instructions say basically fit it all up and apply approx 60psi and see reading. - well I can only get to 15 psi before the guage is reading zero leakage.

I can hear a slight hiss, and a spray of carb cleaner down the inlets shows one valve bubbling a bit.

But seeing as there is so little relative pressure in the cylinder compared to a usual compression stroke I'm hoping I've been lucky and got away with it!

Can those that know confirm for me??

Aladinsaneuk · #15 Post by **Aladinsaneuk** » Sat Mar 10, 2012 10:29 am

i guess you may have got away with it BUT - if it were mine, i would probably do the work anyway to be doubly certain its all good....

(A slight hiss and bubble at a low pressure..... what do you think the internal pressure of the engine would be at full chat? and if it were to fail.... it could well be catastrophic....)