dirtbikedan

Member
Dec 4, 2002
46
0
Hi guys, it seems to me that people with 2 strokes rebuild their top ends about as often as I change my underwear. (quite often that is) lol. Anyway, how many hours do you typically go before a top end rebuild? How many times can you go before a new jug is in order? I just aquired my '99 KDX200 and it seems to have a buzzing noise coming from the engine. I figured it may be a little piston slap/rattle which is normal I'm sure for 2 strokes. (gotta have a little extra clearance in there) But I don't think this bike has had the top end redone since it was new. Thanks guys.
 

dirt bike dave

Sponsoring Member
May 3, 2000
5,348
3
When I had my KDXs, I would do rings every 1,000 miles. Pistons every 2nd or third set of rings. I'm sure many people go much longer with no problems.

As KDXs have mild porting and tend to be trail ridden rather than raced hard, rings seem to last much longer than most bikes. Gotta keep the air filter clean, though.
 

fuzzy

~SPONSOR~
Jul 26, 2002
447
0
This buzzing noise is characteristic of the KDX. Run a full quart of tranny oil to help quiet it down some.

I've seen KDX top ends go close to 4k miles. It all depends on the harshness of use, and quality of lube. I usually get about 2000mi before I can notice a minimal power loss, and re-build at 2500. Do a compression check, but if it runs good then ride it!
 

Mrobbins

~SPONSOR~
Sep 28, 2002
172
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Just returned to riding this year so forgive my possible stupidity. Can you just do a compression test or other test/inspection to find out when it's time to rebuild? I have as used 97 KDX with no idea how many hours/miles are on it.

At least these miles/hours numbers give me a benchmark from after I rebuild it.
 

dirtbikedan

Member
Dec 4, 2002
46
0
Something funny I heard: I called a bike shop recently with a couple questions about what oil to use in my kdx, and he said synthetic was for all out race bikes and conventional oil would have better wear characteristics. hmmmmm...... I run amsoil synthetic anyway at a 50:1 mix. Would it really be better to go with conventional?
 

jc

Member
Sep 22, 2001
57
0
I have a 96' that has never been opened up and a 95 i sold a year or two ago and it was never opened either. I only get to ride two or three times a month on average though but I ride with young guys on 250's and have to work it sometimes. I run only synthetic oil (G.S.) 50:1 92 oct. pump gas. I have a buddy that has a 92 kdx 250 that is getting its first piston this winter. He runs only amsoil stuff. Conventional oil is probably fine for race or trail (as good as they are being made now) but I find for the little extra $ I have had great luck synthetic. Fuzzy is right about the full qt. of oil. It will quiet down the bike with no adverse effects.
 

canyncarvr

~SPONSOR~
Oct 14, 1999
4,005
0
Forget any compression numbers you hear about, get from someone else etc.

There is too much room for error what with different methods, gauges and such.

Where it IS of value is when you compare numbers on YOUR bike that YOU'VE taken over time. Test your new topend after the rings/piston seat, compare that to six months later to get some sort of idea of what's going on in YOUR bike.

'When do I rebuild' can be answered as well as 'How do I jet?' To quote a national brand diaper maker, it all 'depends'.

My first top-end was at the 2year/4000mile mark. My 'C' oem piston measured 2.592", a new 'B' out of the box measured 2.597". But my rings measured only about .015" gap.

A bit of a disclaimer...part of the piston disappearing act may well have had something to do with the ONE tank of stinking belray H1R (HR1, whatever) I ran which seized the bike..taking a bit of nikasil (electrofusion/whatever) with it.

***edit*** Of course, I knew I'd hear about THAT! ;)

Oil certainly matters.
 
Last edited:

KelvinKDX

LIFETIME SPONSOR
Aug 25, 2000
1,622
0
Originally posted by canyncarvr
...part of the piston disappearing act may well have had something to do with the ONE tank of stinking belray H1R (HR1, whatever) I ran which seized the bike..taking a bit of nikasil with it.

Oil certainly matters.

You should use the regular Bel-Ray H1R Synthetic instead of the stinking type. :flame:

btw - i use the H1R in my '99 KDX225 (as i did in my KDX200) without problem (pushing the bike pretty hard).
 

canyncarvr

~SPONSOR~
Oct 14, 1999
4,005
0
I wasn't pushing my bike at the time.

It was actually running...at about 70mph.

I guess THAT was the problem.

Ya. I'll look for the NONstink version
;)
 

Jim Crenca

LIFETIME SPONSOR
Mar 18, 2001
509
0
I promise I'm not intending to open that God awful can o' worms on oil, but, if you search in advanced tech for the last year, you would find that:

* Many people have had filthy engines and elevated wear with Bel Ray and Spectro
* Redline might hurt the brass in a carb
* Amsoil posts are all over the place
* Haven't heard much about Silkolene
* Probably 90% of all riders that posted had very good things to say about Mobil MX2T or Yamalube
* Rich & Eric have good things to say about Mobil & Yamalube

In my mind, there isn't much of a decision to make.
 

KelvinKDX

LIFETIME SPONSOR
Aug 25, 2000
1,622
0
I've used the Bel-Ray H1R since i've had my bike - but have planned to switch over to the Mobil MX2T based on what i've seen people say. Then i came across a deal where a catalog wharehouse was getting rid of things at 50% off so i bought a good amount of the stuff. I still think that when it's gone i will try out the Mobil stuff to see how i like it.


... but let's not get this thead off topic .
 
Jul 3, 2007
1
0
pistons

I have a 1997 cr125r i road it hard for about 1 month then i tried to start it up and it keep backfireing and blowing smoke from the top end so I took it apart and seen my piston had a hole in it i never worked on a dirt bike but that was pretty eazy. Does any body know what could of cuased that :whoa:
 
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