Engine sound decel

As I mentioned get the cylinder cross-hatched with a ball hone to clean it up nice and help the new rings seat in. Good luck!
 
Really??
I would have thought that would destroy the Nicasil(SPL?) coating on the bore.
Its not something ive ever done, im no expert, but my bikes have always kept going.
 
Iv never heard anything good coming of honing a nikasil bore, the coating is sooooooo thin that the bore would take almost all the coating off.
 
yeah everything I have read indicates if the cross hatching is all but worn away its time for a new coating. If not clean it up with scotchbright and continue on.
 
I think the ball hones might be a bit rough on the port edges. Some use them successfully I'm sure. I've used one on a 4stroke and it worked well, but maybe too well for a ported cyl. I use a tool that has a stack of scotchbrite discs on a mandrel. Works OK in cleaning things up but will not touch the nikasil.
 
I've used the ball type hone several times without any problems.
You just have to give is a couple quick blips up and down the bore. Basically, knocking the glaze off.
 
The Nikasil is hard and as gasgasman says all you are really doing is knocking the glaze off with a couple passes in the bore. This helps the rings seat better. I refer to all of the tools as ball hones, but in reality the tool has the little plates with whatever the abrasive is. No damage to the coating. I've never re-ringed a bike without swinging by the shop and having the cylinder "de-glazed" and re-hatched. Use to re-ring my RM125's 2-3 times a season and never had a problem.

update: I talked to my shop and they use the ball (flex) hone on the 2T's. The spring-loaded finger types are not used on the ported cylinders, as those can catch up on the ports and do damage as mentioned. Basically just re-introduces the oil holding cross hatch pattern and doesn't harm the coating.
 
Last edited:
Well everythings been ordered.

S3 Head with 3 inserts. Should bring squish back to around 1.4mm from what I have been told.

Going to lift the jug till the exhaust port and piston are level at BDC and maintain compression and squish by using the head insert that puts me where I want to be.

Should be a happy Gas Gas with a fresh piston and rings and a few small changes. Hopefully the N3EW needle will be here by the time I have it rebuilt and it will be all go again!
 
You know you are going to have to try every needle you own in the damn thing again!! :D

Can't wait to hear the results of the S3 head and inserts, you may need to order a rear fender as a spare just in case you blip the throttle a 'lil too much.
 
I hope not Bailey :)

I think the N3EW will be right on the money. I'm hoping that it doesn't end up using too much fuel as I've been quite happy with the economy I have been getting with my current jetting. About 6L for 70km mixed open and single.

Quick question. When I measure the squish the RB guide says to turn the engine over with the flywheel. Does the gasser run a gasket for the flywheel cover that will need to be replaced?
 
Jak, that noise is no way related to the piston. The engine speed does not coincide with the rapid clacking noise you have. I would look into the kickstarter area. Perhaps in the clutch. For sure look on the right side of engine.
 
I'll be anxious to see how that S3 head helps out when you get it in. I think after mine gets broken in real good I'll measure my squish to see where it is at and likely send it out to RB. Also be interesting to see if your pending work addresses the noise.
 
SwampGasser said:
Jak, that noise is no way related to the piston. The engine speed does not coincide with the rapid clacking noise you have. I would look into the kickstarter area. Perhaps in the clutch. For sure look on the right side of engine.
Click to expand...

The bike has to go into the dealer for its next service very soon. I may run it past the shop owner and see what can be done under warranty. I don't like the odds as he has only just taken the dealership and wouldn't have much experience in what could be wrong.
 
I have the s3 head on my nambo with the silver insert( the lowest) and I stretch my bike to get 60km per tank. My bike is jetted well with a jd red needle. I can't believe the milage you were getting, I wish I could get that milage!! You'll love the power though it's a handful
 
I hope I don't drop that much!! If I can't get 70kms from a tank I'll be right boned.

Ultimately I want to be able to get 90/100km from the tank. This is what influenced the S3 option over specific head work. At least now I have a baseline I can always go back to. From all accounts, everything I have read has indicated that cleaning up the squishband should improve fuel efficiency and consumption.

Have you measured your squish on the nambo? Tried any other inserts? How many base gaskets?

I have the dealer doing the service next week for warranty purposes. I have asked them to investigate the right side cover for any damage or wear re the sound as they'll have the il drained and the bike in the workshop already. I have felt the kick starter slip once or twice and believe it has a few sheered teeth on the shaft. Will be interesting to see what they suggest.

After the bike comes back I'll see where I'm at and should have everything laid out ready for the freshen up!
 
i havnt measured yet, i only have about 20 hours on the new engine, i havnt bothered buying the black or red insert because i cant see myself using anymore than the power i already have. i cant wait to here your review of the black insert though, i dont know anyone thats tried the very high compression insert. should be pretty friggin wild
 
nambo-trev said:
i havnt measured yet, i only have about 20 hours on the new engine, i havnt bothered buying the black or red insert because i cant see myself using anymore than the power i already have. i cant wait to here your review of the black insert though, i dont know anyone thats tried the very high compression insert. should be pretty friggin wild
Click to expand...

Here is Donnies bike.. Setup same as described..

http://www.youtube.com/watch?v=OyrjtmQjnsk&feature=player_embedded

Not sure what his exact compression reading is. But remember I will be adding in about an extra mm of base gasket to set the port timing which will drop compression from where it currently is. Then cleaning it back up with the right insert. Not looking for maximum hp. Just a really nice clean and crisp power delivery.

I'm really only hoping to clean up the pedantic idle setting more than anything. The more I listen to my bike it pulls very nicely from woe to go as it is. Best thing is if I'm not happy I can go right back to where I am now.
 
mrkartoom said:
I'll be anxious to see how that S3 head helps out when you get it in. I think after mine gets broken in real good I'll measure my squish to see where it is at and likely send it out to RB. Also be interesting to see if your pending work addresses the noise.
Click to expand...

x2 for the clutch.
 
Tranny oil drained. RHS engine cover removed. Identified that the kick starter shaft had sheered a few teeth and had kick starter had moved position on the shift slightly (as suspected). Whether this had any impact on the sound who knows? Mr Gas Gas replacing the starter shaft under warranty. Everything else on that side of the engine looks/feels good. Oil was clean.

Will have my bike back mid next week once the parts have arrived and are replaced. Might take it for a light ride to see if the sound is still present.

S3 Head, Piston Kit, and a handful of jetting needles will have arrived in the mean time. Hoping to be able to run 38/40 N3EW1 or 2 and a 175/178 main.
 
Rebuilt

Got a thread over on dirtbikeworld in the gas gas area with pics etc.

To sum it up at 65hrs the piston and ring looked alright. Ring gap came in at 0.4mm and 0.43mm top and bottom respectively. Stock squish was 2.6mm with a 1.3mm gasket stack. The exhaust port was open at BDC.

Reassembled with a wossner piston, ring gaps at 0.4mm. S3 head with black (high high) insert which brought squish back to 1.8mm only, while still using a 1.3mm gasket stack. Might drop the 0.3mm gasket next time round to bring squish a bit tighter. Powervalve was carboned up pretty bad and required some attention/cleaning. Gave the whole exhaust port a working over and smoothed things up significantly. No mirror finish though.

The bike fired to life first kick running a base jetting of 38 N3CH#2 178. Ran a few heat cycles on the stand. Checked everything over. A small coolant leak where one of the hoses hadn't clamed on quite right. Drained cleaned up and and filled again. All is good. Gone over all the bolts again - No dramas.

Did a quick run down the street and back working through the revs. It ran well. Hard to grasp power as I wasn't giving it hard or anywhere near wot yet. Let it return to idle on the stand before calling it a day. Spark was a bit white on one side so may need to bring the AS in a turn or step up a size. Will do some partial plug chops and try the N3EH/N3EW tomorrow.

Engine sound that sparked this thread has definately gone. It sounds the way it should now. Can't say if it was piston related or powervalve related.
 
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