Starting problem when cold

[ducbertus]

Hi Menno,

Although it looks bad, I think you're lucky.
Driving this further would wreck the heads.
exhaustvalve lays very deep in the seat.
When the seat is not to deep burned in it can be reseated.
Check also the valve guide. probably this gone to, as they prone to wear.
As valve setting is clearly gone, you have to check carefully the rockers. All of them.
and of course the lobs of the camshaft for damaging.
so basically a complete overhaul.

Good luck.
Ducbertus (from the eastern part of Holland)

PS. if you need help let me know.

[Tamburinifan]

When all damage is discovered, maybe used ST2 heads is cheaper.
I got 2 w OK valves & seats f just over 100 Eu on eBay.
Only problem is you have to make a tunnel f rev counter drive.
Not to complicated, I`ve had that done.
'I had similar problems on mine, not so severe though.
It also functioned surpringsingly well w compression tested like yours.

[h1a]

Here is an update, i have pulled also the other head to see what i looks like, seems to be in much better condition but even on
this the exhaust valve seems to be leaking a little.

I guess i have stretced the service intervalls beyound the 5000km mark, and the reason for that is when my dealer overhauled
the heads at about 90.000 km he told me i could safely ride 10.000 kms between services. Maybe not a good idea after all...

I measured both the bores and pistons, both seems fine with no scoring or scratches. i measured them to be just outside the
assembly clearance but well inside the wear limit.

I left the heads at my dealer too look at it but from what i could see both intake valves needs a little adjustment but seems
to be ok.
One exhaust valve+seat needs to be replaced, probably also the guide.
The other exhaust valve could probably bee ground back to shape but to be on the safe side i ask my dealer to change both.
For the rocker arms and camshaft im waiting for the dealer to rapport bak what he finds.

The ST2 heads might be the way to go, nothing to find at the moment but i put them on my watch list in ebay.

Thanks again for your answers.
Håvard

[Finnpaso]

Seems quite similar problems, what i have heard many times about "907 bad quality heads(early 90's)" compared to ST2 heads.... Still i am wondering, that, can ST2 heads fitted without problems to 907 engine, cause ST2 have another bore???? Anybody fitted??? ..... I am courious about this!

[persempre907]

Seems quite similar problems, what i have heard many times about "907 bad quality heads(early 90's)" compared to ST2 heads.... Still i am wondering, that, can ST2 heads fitted without problems to 907 engine, cause ST2 have another bore???? Anybody fitted??? ..... I am courious about this!

94 mm. for the ST2 and 92 mm. for the 907.
No problem to fit them?
Ciao

[ducbertus]

I'm gonna build in a ST2 engine in my 907 this winter.
bought this last year in the USA during my holiday and picked up the engine for just over € 400 and it came for free to Holland as a part of shipment to our company.

What I can do is take of one cil head and look for a possible restriction to swap ST2 heads on top of the 907.

ducbertus

[Tamburinifan]

Anybody fitted??? ..... I am courious about this!

I have. See my post above on fitment.
ST2 have different cylinder dia but same heads, all parts fr 907 fits.

[ducbertus]

Hi Gert,

what have you done with the rev.counter drive as theS ST2 has an electric one and the 907 an cable driven one? mounted an other dash?

Ducbertus

[Tamburinifan]

I had a tunnel done, same dash, see my previous posts.