Wrong tool - head job completed now! By rooman (Read 1,121 times)

[rooman]

If you spend all day trying to get to the cam-sprocket bolts and end up needing to take off nearly all the bodywork, just make sure you have the right spring compressor when you finally have the cylinder head on the workbench. Mine was okay for car pushrod valves in the 80's but no go for this 2012 VS125 4-valve head.
The inlet side is all gunged up and the exhaust side completely coked and I had to put it all back together to do another day!
See photo of Sym h6t head from manual.

[JR]

Thanks for the advice rooman !

JR

[rooman]

I'm modifying the spring compressor but until I get round to stripping the motor down again I have a question.



internet image, not my actual head

The orange areas of the combustion "dome" are literally flush with the bottom of the head and not scooped out hollow like the rest of the dome. Is this deliberate squish shape or bad design that a little porting could improve?

[cyborg]

I personally would not touch anything done by Sym,,,those squish shelfs are there for a reason ,,,I'd be looking at the fuel you are using after this and also I'd be looking at the valve seals,,,,,any oil consumption? How many miles on it?

[cyborg]

The only thing I would even consider with this engine is head to manifold match and I doubt it that is " bad"

[rooman]

Oil consumption is low, I'm at 9k km, stop/start city centre short journies.
A little inlet manifold matching will be done next time as well as cleaning inlet side gunge and exhaust side coke.
Very similar to Yamaha cylinder heads.


Strangely enough, I've noticed that putting the valve clearances closer to 0.010 than 0.015 (recommended 0.012 +/- 0.002) has reduced idle speed and pulling power WOT uphill. I'll put them back closer to a tight 0.015 where the motor seemed happier before, just a llittle tappet noise...

Dirty aargh!

[cyborg]

that could very well be the reason for the buildup,,valve tolerances too tight and the valves may be hanging open slightly when hot or the valve seat pressure has been reduced because of tension from the rocker,,,this would explain the loss of power at wot,,

[rooman]

thanks, update soon

[rooman]

Both pairs of valves set to 15 now, she responds much better and idles more correctly, just some tappet noise.
Factory settings are given as 12+-02. Perhaps a symptom of a dirty clogged head?

[rooman]

Wow, this job made me suffer.
When I deemed myself ready to attack the head again, I took a day off on overtime hours. The evening before I stripped off body panels and modified some lugs on the flat floor panel with a cutter so as not to have to take off the whole rear end the next time.
Up early, all the EGR pipes were soon disconnected, pipe, carb and inlet studs also.







The head was transferred to the kitchen where it was warmer than the 5°C in the garage! Here, the valves were taken out and I unfroze my fingers.


Here in Switzerland, most apartment buildings have atomic shelters under the garage, they are actually used by residents as cellars or storage rooms.
So the grinding and matching took place down in our "cave" (french for cellar, UK expat liiving in french speaking region).
The valves remounted and all cleaned.






When I had put all back together, turned it over by hand then by kick, I fired it up only to have a horrible clacking sound. Investigation revealed that the chap who had mounted my winter tyres had oover tightenend one exhaust nut partially pulling out the stud, thus gas leaking. So I dismounted the head again and drilled and tapped a bigger (8mm) hole, installed a 8mm bolt with loc-tite then cut it off with the Dremel to the right length. I drilled out and retapped one of the exhaust nuts which were derusted and painted.
All was put back again and she fired up fine. I've only had time to warm her up in the garage but will test on the road of course. Here she is now ready for the cold season, leg protection for me and winter tyres for her along with a belly full of new 10w40.

[cyborg]

Nice!!!!! thats how it's done baby boy!!!!!!! put your head down and come out swinging!!!!! great repair,,,,