Question about powervalve..

[delvey91]

Ok so just finished rebuilding crm motor with new mains, balancer shaft and bearings etc, have put a new piston in aswell.


One question, is the powervalve meant to make contact with the piston at all when the cables are not attached, as when my powervalve is below the point of the 2 notches lining up the piston rings hit the powervalve a tiny bit when cranking it over by hand :s. on and above the notches is fine and not an issue...

After fitting the cables I have the left hand adjuster all the way in... but when i removed the engine it was set to about half way so

Any ideas people, dont want to start it then have the valve kill the new piston !!

[helisupp]

With my adjusters all the way in the rotor hits the cable threaded end and it looks like yours is too., You need it about 5 threads out to start with.

Any adjuster fully adjusted on anything adjustable is suspicious at best.

Here is picture of mine

[delvey91]

Cheers for the pic, thats one clean motor. Mine looked about the same when removed the engine. I stumped as to why the valve is hitting my piston. thats my main concern. As as far i was aware its set back far enough into the exhaust port to prevent this from happening. There is only 1 piston size for the AR so i cant of fit an oversize one in error..

[Eddie Evans]

If your piston is hitting the powervalve in any position you need to file clearance on the power valve otherwise the ring is bound to catch it resulting in a snapped ring and scored bore..
Remove the cables and take the powervalve out. Look for marks where it has been touching.
Using a file, a large half round is best, ease the marks off the powervalve.
Refit the power valve and gently cycle the engine again.
Feel for it touching and ease any marks each time.
On each cycle rotate the powervalve a little to ensure it clears the piston in all positions.
Once you have clearance polish the powervalve face up and refit.

[Jeram]

paint the powervalve with a light colored paint pen then let the piston scratch it, where its rubbing will be obvious.

a few minutes with a diegrinder will fix it.


if the PV position where it contacts is outside of the normal usage range then you dont really need to worry about it as your PV will never be in that position, it is designed to guy the bore for only a specific range of motion.

[Active Rascal]

Your alignment plate at the back looks slightly out... But only slightly. Have you moved this??

Is the engine out the chassis still? Obviously you will need it out to remove the Pv Assembly. If you can remove your head and look down the barrel you'll get a better idea of what's going on.

[helisupp]

I think it only touches the rings in the postion you show it in the picture, the power valve is " TOO OPEN" in this position causing the lower edge to protrude.

[delvey91]

Engines back out and powervalve off, blimey what a mess, been here about half hour with the dremel getting all the caked on soot off. even though it turned relatively freely there was alot there. Have grinded it a tad too just to be safe from catching... Just waiting for my phone to charge up a bit so i can use the camera....has to be over 30% battery

[delvey91]

[delvey91]

All done.. fired up 2nd kick and is sounding sweet as now! happy days, time for bed now, up at 6 to rebuild a cr125 before 9am...

[helisupp]

So, the engines now making a noise with new bearings fitted, sounds like the old balance shaft has taken out the new bearings.

Even though my balance shaft looked immaculate when removed on stripdown, Liesure Trail do not re-install the shafts due to the shaft causing damage to the new bearings, meaning new bearings and shaft again in next to no time.

Although the shaft may look in good condition it needs to be replaced at the same time new bearings are installed due to such a fine surface finish.

[keith]

I have just had new main bearings and leisure/trail says they havnt touchedvthe balance shaft because there was no sign of wear.
When you say they don't re-install the shafts' hat do you mean?

[helisupp]

Keith,

The balance shaft bearings are one of the rarer type of bearings that are not completely caged, the rollers run directly on the precision ground balance shaft, any abrasive debris in the gearbox oil will destroy the bearings (especially if its been full of mud like this one seems to have been).

If you need to change balance shaft bearings due to wear or noise you should change the shaft, its false economy not to.

My bearing was worn so new shaft installed at same time, the shaft looked like it was in great condition, but if you can see any wear or marks just replace it, its a cheap item whilst engine is apart.

As you say yours were not worn and your engine was not in for a full overhaul so it was not an issue, but if the bearing was worn you would have had a new shaft installed. Your engine was in LT same time as my spare engine, but mine was in for a full overhaul and they were instructed to change "every single bearing" and anything else they did not like the look of, hence you would have had a smaller bill.

[garyd]

Ha giving the LT pirates a "free for all" on your engine,would have had em laughing all the way to the Leeds,biggest feckin robbers in Nottm,nay,Midlands!!

[keith]

Just got bike back' and l/t have put new balancer shaft bearing.
So no more noises' bike now runs as it should. Although any engine work that needs doing in the future I'll do myself.