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


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Old 10-28-2012, 10:14 AM
swazi_matt swazi_matt is offline
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Default Top end tips and powervalve?

Just about to do my top end since it is my first on the GG I would appreciate some tips of what to look out for. Have already noted that I need to grind down my socket to fit the cylinder head nuts

Also seen that my pv has some slop so will go through the thread on that, but also noted that the pv shaft moves a bit from side to side is that normal or does it also need to be checked - I am sure I saw a YouTube vid of someone shimming it but not sure

Any good YouTube links will be much appreciated thanks


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Old 10-28-2012, 11:59 AM
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Default Me too

I'm coming up on my first GG top end, my PV needs love also as it sticks open once in a while. I did my wife's GG 200 top end but that was 10 yrs ago, my brain doesn't work that far back

I'll be watching this thread

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Old 10-28-2012, 12:42 PM
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I never had to grind any sockets to get the head off. Some people may need to grind down a ring end spanner to remove the front cylinder head bolts (depending on brand and clearance).

Drain the coolant at the pump first. Then remove the plastic connection that joins the head. You can leave the hoses attached. The rads can be left on the bike, but will need to be loosened at the top and bottom bolts removed to allow them to move forwards.

Remove the powervalve while the cylinder is still on the engine. Much easier to pull it out. Be careful not to pull up on the actuator arm (although not so much a concern if you'll be retensioning anyway). The side to side clearance of the valve can be changed by shimming the assembly. Make sure you clean the assembly up really well, and that you leave some play as it does require clearance for carbon buildup. If its not noisy then I wouldn't change it.

Squish clearance, gasket stacks, port timing. Read up. Now is the perfect time to have the head worked.

Measure your ring end gaps of the old ones to gauge the wear on them. Set the new ones by using the Wiseco calculator. For a 300 you're looking at around 0.4mm to 0.5mm. Use the piston to push the ring down in the barrel before measuring. The cylinder can be cleaned up by using WD40 and a scotchbright pad to remove any glazing. Then wash down with detergent. Inspect for wear/damage. Ideally you'll have an engine rebuilder measure the bore to determine if its still in spec and what size piston to use. Others will have more info on this.

Consider cleaning up any casting slag from the ports. You don't want to mirror finish or knife edge anything. You can polish the exhuast port to a mirror to help reduce carbon build up if you have time on your hands. Make sure not to grind too close to the nikasil coating. It may chip off and you'll be up for more $$.

Inspect carb boot/intake manifold for any signs of perishing or cracking. Pull the reed block out and inspect petals for wear.

The bottom end can have some side to side movement but should have zero play up and down.

With gaskets a light blow with a rubber mallet can help to break covers/parts free without damaging the gaskets. Make sure you replace the head o-rings and cylinder gaskets with fresh ones. Others can probably be reused if not damaged. A light smear of grease on them when installing means they'll come off easier next time and also helps to hold them in place during installation. Trim the base gaskets if required. You don't want any excess gasket blocking off any ports.

Thats all I've got for now. Heres the thread I ran while doing my last one. Probably goes into way more detail than you need.
http://www.gasgasrider.org/forum/showthread.php?t=11970
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Old 10-28-2012, 12:47 PM
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And dont forget to have the bike spotless before starting work. I also find that spraying the frames etc with your fav lube (inox/wd40,etc) will stop any dust or dirt you may have missed from dropping off the bike.

Hold the rod as you take the cylinder off to stop the piston slamming forwards or backwards against the cases. Stuff the cases as soon as you have the clinder off.

Read up on how to install piston clips. Practice on the bench a few times with the old ones before going into action on the fresh slug. I like to install one clip on the bench to limit the time mucking around with clips above the engine.
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Old 10-29-2012, 12:58 AM
swazi_matt swazi_matt is offline
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Thanks will follow your advice, unfortunately do not have the time to get head/squish sorted and looks like the base gasket I have from the kit is thinner than what was in there :-/

Also the gasket kit I got sent was missing the gasket for the plastic coolant connector and that is the gasket that got torn, I will try my best to get it back in but any tip here?

Lastly how would I know if I have dislodged any of the balls in the pv governor?
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Old 10-29-2012, 01:17 AM
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If you've dislodged a ball you'll probably find that the PV arm will not sit where its meant to. I haven't experienced it though so not 100% sure.

Get some nice thick gasket paper and attempt to cut your own, or contact one of the dealers on the site and see if they'll send you one out. I have a spare one here if worst comes to worst. Don't know how long it takes to post Aus to South Africa, and it sounds like you're running short time.

If you're not going to have any of the head machined you still have options. Putting in a thinner/smaller stack of gaskets will reduce the squish and raise the compression. This will favour bottom end to mid both with the port timing and with the CR. You just don't want to go so far as to inhibit the top end, or end up with fuel supply issues/pinging. I'd probably take the time to at least take a squish measurement and measure the gasket stack you are using. From there someone can probably at least estimate your CR.
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Old 10-29-2012, 03:01 AM
swazi_matt swazi_matt is offline
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thanks, was thinking of cutting a gasket. I will be going to SA a week before the roof to get my tires etc for the race (race purely in technical terms, more a survival ride!) so will be able to get a gasket etc if needs be, just dont really want to be stripping down again then.

suppose i will know if i need thiscker base gaskets once i ride the bike

Also figured that since i have the side cover off for the PV correction i may as well check the condition of my clutch plates, have seen the specs in 06 were 2.75-2.85 (min of 2.68) do you know if these have changed?
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Old 10-30-2012, 02:48 AM
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tip for getting the head orings to stay put - add a little grease to the groove, helps stick them in place
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Old 10-30-2012, 03:14 AM
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Quote:
Originally Posted by swazi_matt View Post
tip for getting the head orings to stay put - add a little grease to the groove, helps stick them in place
Yep. Some of them like to be gently and evenly stretched a little prior to installation as well.
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Old 10-13-2014, 04:31 AM
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the stock orings stock are 101,32x1,78 and 72,7x1,7 ones i can get are 101.34x1.78 and 72.76x 1.78
will these be fine
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