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Old 06-20-2012, 08:52 PM   #16
innathyzit OP
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Quote:
Originally Posted by Padmei View Post
Excellent lil reply old no.99. So the 4 valves pushed more mixture thru in a smaller area of the combustion chamber & a better detonation happens in a 'squarer' chamber?

Why are the valve recesses there on top of the pistons? if the cam etc are timed right there shouldn't be any chance of the valve hitting the piston. Am I right in guessing that the space in the cylinder is limited perhaps due to a short stroke & the further the valve opens the more mixture can pass thru however the only place to gain depth for the valves is the top of the piston? Rotary valves or sliding valves no good?
Wouldn't the valve recesses affect the efficiency of the combustion?
If the valves open further then they will allow more air/fuel to enter but piston to valve clearance is harder to achieve so valve recesses and dome shaped pistons need to be used so a decent copression ratio is achieved. The other way is to have a cam with a long duration but again compression ratio is affected because the valve is also closing later therefore there is less volume of fuel/air mixture (e.g.the piston is further up the stroke when the valve closes) to compress to achieve decent compression so generally pistons are domed.

Yes there are a lot of compromises in engine design.
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Old 06-21-2012, 01:57 AM   #17
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Thanks I went & did a bit of research after posting & learnt a lot.

benelli content


When I first saw that pic I thought it was some kind of dogs face???
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Old 06-30-2012, 03:48 PM   #18
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Don't panic, haven't lost interest, just a little angry with myself for being a dum ass.

Made a new gudgeon bush up yesterday with my new lathe tool set (don't tell Mrs Woodman). After machining up the bush and polishing it all smooth I took it out of the lathe and went to fit it into the small end and that when i realised that I had machined it for clearance instead of interference. Still have some stock bushing left so will try again today, or take the KLR for a hoon. Probly this.

Another issue discovered yesterday was that the benelli small end is wider by about 4mm than the distance between the gudgeon bosses on the xr piston. Dremmel time. Padmei? did you have an electric dremmel?

Anyway not major issues , just annoying challenges .
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Old 06-30-2012, 11:08 PM   #19
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Bugger.
How much do you allow for interference fit? a thou or same dia?

Yep I've got a ryobi dremel machine thing. i'll drop it out to you with your welder - i'm gonna buy my own one.
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Old 06-30-2012, 11:35 PM   #20
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Originally Posted by innathyzit View Post
Don't panic, haven't lost interest, just a little angry with myself for being a dum ass.

Made a new gudgeon bush up yesterday with my new lathe tool set (don't tell Mrs Woodman). After machining up the bush and polishing it all smooth I took it out of the lathe and went to fit it into the small end and that when i realised that I had machined it for clearance instead of interference. Still have some stock bushing left so will try again today, or take the KLR for a hoon. Probly this.

Another issue discovered yesterday was that the benelli small end is wider by about 4mm than the distance between the gudgeon bosses on the xr piston. Dremmel time. Padmei? did you have an electric dremmel?

Anyway not major issues , just annoying challenges .

LOL..
Wasn't hot when yer done the final cut was it..
then shrunk when it cooled..

I have done that before... wonder why the bearing suddenly be come a lose fit..
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Old 07-01-2012, 12:55 AM   #21
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Bugger.
How much do you allow for interference fit? a thou or same dia?

Yep I've got a ryobi dremel machine thing. i'll drop it out to you with your welder - i'm gonna buy my own one.
chur bro, not too worried about the welder though. thou and a half seems to work from memory.


Quote:
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LOL..
Wasn't hot when yer done the final cut was it..
then shrunk when it cooled..

I have done that before... wonder why the bearing suddenly be come a lose fit..

No, just subtracted instead of added. Made and fitted another bush this arvo, had to make a wee jig to wind it in as the crankcases are all assebled up. Went well and didn't need to hone the bush to suit the gudgeon so got that right. Made and fitted the bronze valve guides too.

Was too cold for a ride.
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Old 07-01-2012, 02:33 AM   #22
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Was too cold for a ride.
Pussy...
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Old 07-04-2012, 02:57 AM   #23
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Pussy...
Time for another snow ride.

Inwood Lookout is close by...

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Old 07-04-2012, 05:45 AM   #24
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Time for another snow ride.

Inwood Lookout is close by...

Sounds good to me, but better get over this orrible cold first.
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Old 07-04-2012, 01:12 PM   #25
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but better get over this orrible cold first.
its a real fooker isnt it
perfect riding weekend last weekend and Glen and I were way too crook to ride - what a waste
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Old 07-05-2012, 12:13 AM   #26
NordieBoy
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Pussies!
It was 24* last weekend!
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Old 07-05-2012, 12:28 AM   #27
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Pussies!
It was 24* last weekend!
Not up at the lake where the real men (idiots) were VMZing in the snow.
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Old 07-05-2012, 02:57 AM   #28
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Not up at the lake where the real men (idiots) were VMZing in the snow.
Just been looking at the pics.
https://plus.google.com/photos/11444...wa&gpsrc=pwrd1

That would have been fun on the 705's
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Old 07-05-2012, 03:43 AM   #29
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Not up at the lake where the real men (idiots) were VMZing in the snow.

Did you see in the paper who was the main naming rights sponsor for the series again this year?

Please say yes.
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Old 07-05-2012, 05:01 AM   #30
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Wouldn't be that Mot Repco outfit.

Too dodgy.
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