Engine noise

[roostafish]

This weekend I rode with Jefro820. His bike is only a couple rides old, and it sounds so tight, and quiet. My exhaust is nice and quiet, but there's more mechanical noise emanating from my engine. I begin to wonder how much of that means that I need to do a teardown and complete rebuild. Or, with only 2000 miles on the bike, should I just do a top end?

 

[webmaster]

What kinda noise you hearing? It always had a bit of powervalve "whack" when they open and close - and a chat-chat-chat if you get it right in the zone where it is open-close-open, etc.

jeff

 

[roostafish]

Nothing bizarre, just general "mechanical" noise at idle and while riding. Pulling in the clutch makes no difference. It almost has that worn clutch basket sound, but clutch engaged or not makes no difference in sound.

I think, with 2000 miles on the bike, it's high time for a piston at least. I just have ridden it so little, that 2000 miles has snuck up on me. I was thinking that perhaps GasGas has improved their tolerances over the years and the new ones are just super tight and quiet. But I don't want to excuse not doing regular maintenance either.

 

[Jeffro820]

Roostafish, you can't compare the two. My bike only has 4 rides on it (maybe 9 hours of engine time & the nipples are still on the crappy knobby tire!), yours has......well, you know, it's been ridden. If & when you do the top end, bring it over to the casa. Or at least I'd like to help you with it....mine will be behind you a bit!

After buying the Gasser, the dealer (Gary) told me to expect it to be tight for 10 or so hours of motor time...and not to freak out if it doesn't sound "like your other bikes" after a month. That is dead-on.

When I rode your bike, the engine noise was not any more noticeable that my past bike (RM) or Jeff C's KTM 300. I gotta say your carb was dead on, that's what I want! I need to tweak my pilot a bit.

Any way...good ride.

Jeff

 

[roostafish]

I'm using an LTR jet kit. I don't remember the numbers, but next time we're out, or if we do a top end, we'll take the carb off and look at them. The needle is the big deal. If you continue to have jetting concerns, doing the squish band mod will get you there, guaranteed. Besides that, it makes the bike run really really really good.

 

[PEB]

My 99 made what I would consider a normal amount of noise. A little bit of clutch whir and only mild vibrations.

My 02 made very little clutch noise and about the same vibrations. When I rebuilt it I took a couple hours and played with the postion of one of the main bearings taking the time to get it postitioned such that the crank was perfectly centered in the cases. Once i had it back together it made hardly any vibrations and was really smooth, Myron are you still running that engine?

My 07 makes a fair amount of clutch whir and had as much vibration if not more that the 99.

I wonder if there is a way to balance the clutch to cut down on the whir. I have not done a bottom end on the newer roller bearing cases yet, I wonder how much tolerance there is for side to side positioning.

The skid plate makes a big difference as well. My plastic Hyde is alot quiter that the alumuninum ones I used to run.

 

[roostafish]

Hmmmm. I like this positioning of the crank of which you speak. How on Earth did you do that without smacking and sideloading the crank bearings?

 

[einsteingarage]

This is an easy fix...........Don't ride with jeffro and your bike will sound fine.

 

[JEEPUSAURUS]

Paul, I'm still running that engine, i've put rings in it since then but thats it, and yes very smooth, and very little vib, i swapped with my buddy so he could ride it, and i thought there was something wrong with his KTM 300, that thing vibrated, not something i'm used to.

 

[GMP]

The newer engines use a two piece ignition side roller bearing (like KTM engines), vs. the ball bearings on the older bikes like roost's bike. These bearings run, by design, at a greater clearance and therefore may (will?) cause slightly more vibration.

As far as the crank positioning, it should be done by drifting the crank in the bearings, not the bearings in the cases. Some older bikes like my '00 had a very loose fit and the crank would float in the bearings, eventually wearing the journals even more and requiring replacement. This was a problem on some cranks in '99-'00.

If you want to split the cases and rebuild the lower end, measure the total clearance between the crank wheels and the cases(the sum of both sides). When you assemble the motor, divide this by two and place a feeler gauge of this dimmension in the case for the crank to seat against when you fit it in on the primary side. This will give you an approximate center with no tapping on crank to adjust later. This is how I do it, not neccessarily a documented procedure.

FWIW, I always use heat/cold instead of force to assemble an engine. Warm the cases in an oven and freeze bearings with dry ice, it will go together with much less trauma. Same with the crank, warm the primary side case with the new bearing, freeze the crank, and it will fall right in.

Hope this helps.

 

[PEB]

Glen, I found on the 02 I had to float the clutch side bearing to get the crank centered. The 99 i rebuilt i didn't try to center.

The ignition bearing sits all the way in the cases with the outside face of the bearing up against the case. The clutch side bearing sits out a around a half mm from the cases leaving what I presume to be an "adjustment".

When I tightned the clutch end of the crank, the crank would walk through the bearings untill it came up tight to the inner race. I remember the little POP fom when I did the 99 and it did it again on the 02. I tore it down and figured out how much I wanted to move the bearing. I baked the clutch side case just long enough to get it hot, and then with tiny taps of the case on a cookie sheet I got the bearing to wiggle down to where I wanted it. On reassembly when the crank moved a tiny bit it moved to where the clutch side bearing sat and came out almost exact. Had I acccounted for the gasket squishing it would have been closer.

I think alot of vibes come off the clucth. Is there a way to balance it?

 

[GMP]

Paul,

Good point and makes a lot of sense in your case. On my '00 though, there was distinct axial play in the assembed motor. You could pull/push the crank in and out by the flywheel over 1mm, and hear a clunk as it hit each side. When I tore it down, the bearings were a very tight fit in the cases, it was the crank that was moving. Tolerances I guess. Another way would be to seat the bearing fully, and add a shim(s) between the crank and inner race.

When I rebuilt the '01 XC125 I was able to drift the crank as well. On that motor, the primary pinion is splined to the crank, so I imagine the force of the nut being tightened is not against the bearing inner race, but probably against the spline shoulder. Interesting enough, it had the same problem as my '00 250, loose crank journals. They were slightly blued from heat when torn down. A GG 125 crank is a rare and expensive specimin, so we had it plasma sprayed and remachined.

As far as the clutch vibes, could the dampers be loose? I think mine is perfectly normal and typical, better than a KTM for sure and better than a Husky 250.