RM125 rattle

queen of spodes
Edited Date/Time 1/27/2012 12:40pm
When I chop the throttle on my RM125 I'm hearing a new rattle just as the motor winds down to idle. I'm used to hearing the normal piston slap of two strokes, and this new noise is on top of that. The top end was rebuilt about 20 hours ago with a new Wiseco piston & rings. The pipe is tight.

Would a loose bottom end make a sound that is similar to piston slap, just off of idle?
|
ratonmacias
Profile picture for user ratonmacias
Posts
1041
Joined
4/1/2008
Location
Guadalajara MX
ratonmacias 8/2/2011 7:28am
8/2/2011 7:28am
have tried the same with the clutch pulled in? does it rattle the same way?
xnationalwrench 8/2/2011 8:24am
8/2/2011 8:24am
Check and see if you have movement at the crankshaft (back & forth) it might be bad main bearings
queen of spodes 8/3/2011 10:26am
8/3/2011 10:26am Edited Date/Time 8/3/2011 10:27am
@Raton.. yeah, same noise.

@all: I'll tear into it later this week. Will let you know what I find!

The Shop

See All »
GsxR1000Ryda 8/18/2011 3:47pm
8/18/2011 3:47pm
my 02 rm 125 is making a similar noise. sounds like its coming from the crank too.
mxtech1
Profile picture for user mxtech1
Posts
1957
Joined
7/21/2011
Location
Galesburg, IL US
mxtech1 8/19/2011 7:01am
8/19/2011 7:01am
Crank bearings are probably wearing.

Pull the stator cover off. grab the end of the crank and see if you can feel any play in the brng
queen of spodes 10/3/2011 10:59am
10/3/2011 10:59am
No play in the crank. Someone else listened to it yesterday and said it sounded fine for being 10 years old. Another guy said it sounded fine on the track and on the stand.

Probably going to order a new piston kit to be on the safe side.
Gukamonster
Profile picture for user Gukamonster
Posts
526
Joined
3/23/2011
Location
Gigantic CK
Gukamonster 10/4/2011 1:50pm
10/4/2011 1:50pm
Is there any play in the clutch basket? If it's not that it sounds like impending bottom end troubles, assuming the top end is still fairly fresh. There could be some microscopic flaws in the cylinder walls too.
queen of spodes 10/5/2011 10:19am
10/5/2011 10:19am
Haven't pulled the cover off to check. I just ordered a new Wiseco pro-lite piston kit. When I have the jug off I'll check for play in the crank. Hoping not to have to tear the entire motor apart.
queen of spodes 10/8/2011 5:10pm
10/8/2011 5:10pm Edited Date/Time 10/8/2011 5:20pm
Well, I discovered the source of my piston slap. At the car wash I noticed a lot of buildup around the plug. Took the cap off and the plug was loose by a half turn. Sad

Got it home and stripped it down.


Head:


This top end had no more than 15 hours, none of that race time.


Some other views of the piston:




Bottom end, here I come. Sad
queen of spodes 10/9/2011 9:26am
10/9/2011 9:26am
Since there was no play in the crank and the cylinder looked great I went ahead and put it back together this morning. Started it up and the slap has quietened down quite a bit. Sounds like a new bike again.
Cancerman
Profile picture for user Cancerman
Posts
756
Joined
7/16/2011
Location
In Hell, FL US
Cancerman 10/9/2011 2:38pm
10/9/2011 2:38pm
There is a lot of blow by all around the piston, I would check the new piston / cylinder clearance before I buttoned it up. The plating may be worn. That's alot of blowby for 15 hours. You can measure the ring gap and see how worn out the ring was. I just finished my 02 yesterday.
queen of spodes 10/9/2011 5:12pm
10/9/2011 5:12pm
Too late to check the gap now.. I should have done that when I had the jug off this morning. I suppose the next time I have to do the top end I'll look at boring and replating.. or maybe using the 134 kit from Eric Gorr.

Had fun at the track today. It's amazing that someone as slow as me can get so worn out riding. Getting old sucks!
Cancerman
Profile picture for user Cancerman
Posts
756
Joined
7/16/2011
Location
In Hell, FL US
Cancerman 10/9/2011 10:23pm
10/9/2011 10:23pm
How old is old? I'm 53 with Cancer. Talk about feeling old and tired! I'm going to attempt to ride Hard Rock next weekend with the RM 125 & 250, and do some testing and set up. 1st time on a 125 in 20 plus years! If all goes well, I MAY attempt to race the following weekend. I'll let you know how bad (or good) it goes.
queen of spodes 10/10/2011 10:44am
10/10/2011 10:44am
Early 40s here -- kudos to you for sticking with it. I knew of a guy in N. Georgia with cancer - he built a track and rode his ass off. I'd do the very same thing as long as I was able.
queen of spodes 10/23/2011 7:52pm
10/23/2011 7:52pm Edited Date/Time 10/23/2011 7:53pm
Small update. Bike is still running great as of about 4 hours on the new top end.

This weekend I installed a Boyesen RAD valve I found on Ebay for $50 and am very happy with the results. The bike was all top-end and now has good power in the middle to top, just the way I like it.

Pit Row

See All »
Jakes
Profile picture for user Jakes
Posts
50
Joined
3/23/2011
Location
Indiana, PA US
Jakes 10/30/2011 6:32am
10/30/2011 6:32am
Are you putting your top end together with oil on the piston and rings? If so next time put it together dry and you will notice alot
less blowbuy from the rings sticking in the lands. An old tip from Harry Klemm.
queen of spodes 10/30/2011 7:06am
10/30/2011 7:06am
I've always used a dab of oil on the piston/rings.. I guess I picked up that habit from the old clymer books.

How are you breaking in your bikes? I usually warm it up, then shut it off and wait till it cools down. After that I take it easy after the next warm-up for a few minutes, then ride like usual.
Jakes
Profile picture for user Jakes
Posts
50
Joined
3/23/2011
Location
Indiana, PA US
Jakes 10/31/2011 3:41pm
10/31/2011 3:41pm
Yep that sounds like how I break in a fresh top end. I read an article by Vic Krause that told the story of two top ends replaced on a YZ 125 by Mr Klemm. One dry and one with oil on the rings and skirt. After a short run at rpm the oiled top end showed blowby and sticking rings. The dry top end showed none of this and no I'll affects. All the oil your piston needs is already in the fresh fuel charge. I tried this and will never go back to the OPEC way. Cheers!
Dnlp D952
Profile picture for user Dnlp D952
Posts
126
Joined
8/6/2011
Location
Boonville, IN US
Dnlp D952 11/5/2011 8:06pm
11/5/2011 8:06pm
queen of spodes wrote:
Too late to check the gap now.. I should have done that when I had the jug off this morning. I suppose the next time I...
Too late to check the gap now.. I should have done that when I had the jug off this morning. I suppose the next time I have to do the top end I'll look at boring and replating.. or maybe using the 134 kit from Eric Gorr.

Had fun at the track today. It's amazing that someone as slow as me can get so worn out riding. Getting old sucks!
Tell me that's not rust on your chain...Huh
queen of spodes 11/6/2011 6:45am
11/6/2011 6:45am Edited Date/Time 11/6/2011 6:46am
You haven't ridden in red clay much have ya?

Edit so this is easier to understand. The track is good old Georgia red clay. It's dry in spots so the red clay becomes dusty and sticks to the chain which is properly adjusted and lubricated before every ride.

Post a reply to: RM125 rattle