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Enduro Engine - 2 stroke Cylinder, Piston, Tranny, Bearings, Clutch, Pipes & Silencers, etc.


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  #11  
Old 09-08-2017, 11:17 PM
rossi rossi is offline
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On one of my GG 250 heads the spark plug was drilled a degree or 2 off perpendicular which was a nightmare to cut the face for squish. I wonder if they mill the heads at the factory with a 4 jaw chuck or some tool that holds the head from the head stud holes?
That sounds like mine, looks ok from the top but when you look at it closely the hole is clearly not central inside the dome.


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  #12  
Old 09-09-2017, 03:55 AM
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I've been trying to think of a clever way to build a mandrel to tool. But it doesn't make machining he face possible.
If you search different country's wreckers people must have another head and pretty small to post.
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  #13  
Old 09-09-2017, 03:35 PM
rossi rossi is offline
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For the moment I have removed 0.86 cc from the head by filing some Singh grooves copying Motopsycho's pics. I have crunched the numbers and removed base gaskets to set the squish at 1.5mm which should hopefully be OK. It turns out that my squish was originally even wider (2.2mm) as I had been been using a vernier to measure the piston depth and the height of the flange on the head, but discovered my vernier is out - measurements now taken properly with a micrometer and solder.
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Old 09-09-2017, 06:38 PM
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Yeah the squish is a wedge shape just to make it worse.
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'07 EC300 GG
'14 TXT250 GG
'? 496 CPI Cheetah RZ/RGV hybrid
'22 765 Street Triple RS
'21 XTrainer
'69 Stinger T125 Suzuki
'23 TRS 250RR (it's a Trials thing)
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  #15  
Old 09-09-2017, 08:48 PM
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Originally Posted by (F5) View Post
I've been trying to think of a clever way to build a mandrel to tool. But it doesn't make machining he face possible.
If you search different country's wreckers people must have another head and pretty small to post.
I just bought a nice steel piston stop and am using it as a mandrel.
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  #16  
Old 09-10-2017, 03:44 AM
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4 jaw chuck and DTI it up off set so be it. Man I'm stoopid
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'? 496 CPI Cheetah RZ/RGV hybrid
'22 765 Street Triple RS
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'69 Stinger T125 Suzuki
'23 TRS 250RR (it's a Trials thing)
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  #17  
Old 09-17-2017, 11:53 AM
rossi rossi is offline
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Update -

With the Singh grooves filed in the head removing 0.8cc the engine is now running with a single 0.3mm base gasket.

Less than ideal for the height of the exhaust port, and slightly greater than 1mm squish but is it like riding completely different bike. Torque off the bottom end is fantastic and it pulls seamlessly into the power band.

Running 50:1 98 RON (Euro) with motorex fully synthetic, the central plug insulator is a perfect match for a bar of milk chocolate and absolutely no sign of detonation.

Fuel range is improved - I haven't done more than 1/2 a tank in one go yet but it looks like it will be good for close to 100km. Jetting is also consistent from 0 - 2000 m (N1EF#1, 165, 35)

I'm not sure why but the bike also seems to be a lot smoother with less vibration through the footpegs

The only gripe is the burble on the transition between closed and partially open throttle which makes the throttle an off / on / more affair rather than feeding in smoothly on the initial opening. Now that everything else is working I can experiment with the needles though.
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Old 09-18-2017, 06:19 PM
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Quote:
Originally Posted by rossi View Post
Update -

With the Singh grooves filed in the head removing 0.8cc the engine is now running with a single 0.3mm base gasket.

Less than ideal for the height of the exhaust port, and slightly greater than 1mm squish but is it like riding completely different bike. Torque off the bottom end is fantastic and it pulls seamlessly into the power band.

Running 50:1 98 RON (Euro) with motorex fully synthetic, the central plug insulator is a perfect match for a bar of milk chocolate and absolutely no sign of detonation.

Fuel range is improved - I haven't done more than 1/2 a tank in one go yet but it looks like it will be good for close to 100km. Jetting is also consistent from 0 - 2000 m (N1EF#1, 165, 35)

I'm not sure why but the bike also seems to be a lot smoother with less vibration through the footpegs

The only gripe is the burble on the transition between closed and partially open throttle which makes the throttle an off / on / more affair rather than feeding in smoothly on the initial opening. Now that everything else is working I can experiment with the needles though.
Needle will fix it now.

Been posted numerous times.

Squish, float height, jet and forget..

I chased myself around in circles for a long time before I worked it out. On my 2013 the head was sent off immediately following the break in ride.
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