4S top end rebuild w/o engine removal from frame ?

AJSB

Member
Joined
Mar 11, 2001
Messages
14
Likes
0
#1
Did you notice how i just love to do weird questions ? So, brace yourself for this one...

I was talking with another rider about 4S vs 2S and a interesting subject was the following:
Usually for a 4S you need to remove the entire engine for a top end rebuild ?
I know that 2S dont need that and because 4S engines weight more and are more squeezed between the frame, the removal of a 4S engine
should be a PITA if you need to remove it for a top end rebuild and you are all alone on your own in a DIY style.

OTOH, i heard that YZ/WR 250/400/426 F can have a top end rebuild w/o engine removal of the frame...is that correct ?

...and what more 4S engines dont need to be removed for a top end rebuild ?
How about the Huskys TE/TC 400/410/570/610 ? Bergs 400/501/600/650 ?
KTM LC4 6x0 or RFS 400/520 ?
Suzys DRZ 400x/250 ?
Can any of them also be top end rebuild w/o engine removal from frame ?

TIA


------------------
Amandio J.S. Bacalhau < '96 KTM LC4 620 >
 
Joined
Jun 16, 1999
Messages
693
Likes
0
#2
The new Yamaha racing four-stroke engines can be rebuilt while still in the frame. You can even rebuild an XR400 motor without taking it out, too. Not sure about any euro thumpers, but I'm guessing most new four-strokes are the same way.

------------------
Kevin
1999 XR600R
badassxr600r@aol.com
 

PK

Member
Joined
Feb 27, 2000
Messages
54
Likes
0
#3
I currently have the top end off of my YZ400 for a rebuild, awaiting parts UGGHHH. The KTM's can be done as well with the motor in the frame. The main difference, 4 vs 2 stroke, is pulling the cams, other than that it is not much different that a 2 stroke. It may intimidate you a little bit but I would say it took 20 minutes longer to yank the top end of my thumper than it does to do the same job on a 2 stroke. I also had a vavle that needed a smaller shim to bring it back to spec, but that was a 5 minute deal. Even after yanking the motor apart, I found out that I could have put another year of riding on the bike as everything was still in limits.

Pat
99 YZ400
 

AJSB

Member
Joined
Mar 11, 2001
Messages
14
Likes
0
#4
Originally posted by PK:
KTM's can be done as well with the motor in the frame.
PK:
Are you talking about the LC4 400, LC4 6x0 or the RFS engines ?
I looked to my engine head cover and the gap seemed too small to raise the head cover
and pass it over the camshaft sprocket used
by the camshaft chain...i almost bet that with
the LC4 400 and maybe the 400 EXC/SX can be done (more space because of smaller
stroke) but with the real big bore KTMs im
affraid that there isnt space enough to remove the head cover w/o risking to damage/force anything.

Can you clarify this ?

TIA


------------------
Amandio J.S. Bacalhau < '96 KTM LC4 620 >
 
Joined
Aug 22, 2000
Messages
527
Likes
0
#5
The easiest way to figure it out is by looking at the cylinder studs. If the head is held onto the cylinder, then the cylinder bolted to the cases, you can probably get it apart without removing it from the chassis.

If the studs go clear thru from the head to the cases, you've gotta yank it out of the chassis.

Hey, for you big burly dirt bike riders, what are you worried about anyway? Even a big four stroke engine doesn't weigh much more than 50 lbs (most are much less). C'mon, don't get wimpy



[This message has been edited by DualSportr (edited 04-05-2001).]

[This message has been edited by DualSportr (edited 04-08-2001).]
 
- a d v e r t i s e m e n t -