hy after all this time and posts ive narrowed it down to a nocking piston so im goin to change it with a friend but just have a querie he said you have to take engine fully out to change piston is this right or do you do it in bike and how will i find out the settings for the cam chain and tappets i dont think there in manual regards ste

Changed 280 back to 250 with engine in frame but very tight and had to tilt engine on its mounts.

Comes to bits ok but struggled to get it back together in the frame.

Hi, Should be fine in situ.

Give me a ring if you have any problems.

Regards,

Caroline

I removed a 4RT top end recently, and left the engine in the frame. But I found it was easier -- and probably safer for the head cover mating surface -- to rock the engine forward. With the bike on a stand, I took out the lower rear engine mount, loosened the swingarm axle (but left in place), removed the bottom sump guard bolts, loosened the front sump guard bolts, and removed the 4 "down tube" mounting bolts. Then the engine could be rotated forward. I placed a rod (it's a T-Handle in the photo) through a down tube mounting hole to hold everything in the rotated position. See photo below:

Edited January 10, 201115 yr by SportSawyer

I removed a 4RT top end recently, and left the engine in the frame. But I found it was easier -- and probably safer for the head cover mating surface -- to rock the engine forward. With the bike on a stand, I took out the lower rear engine mount, loosened the swingarm axle (but left in place), removed the bottom sump guard bolts, loosened the front sump guard bolts, and removed the 4 "down tube" mounting bolts. Then the engine could be rotated forward. I placed a rod (it's a T-Handle in the photo) through a down tube mounting hole to hold everything in the rotated position. See photo below:

hy thats great help thanks im a novise but want to try and strip it myself so i can learn the only probs is the tappets and cam chain how do i reset these and can i strip it down to see if i need a barrel and worry about the cam chain and tappets when rebuilding regards ste

Tappit adjustment is in the manual as is cam chain adjustment/setting.

You need to make a little tool as per diagram to release tension on the cam chain. There are marks then on cam shaft sprocket when rebuilding.

Worth taking off the bash plate and side front frame arms as a matter of course. You will need to support the bike via the back frame cross member or footrests to allow engine to drop slightly lower.

Careful when installing cam guides into bottom end of engine as can miss bottom locating lug.

Drain rad etc first.

All fully documented in engine rebuild section of the manual.

If you get stuck I'm sure there are enough people on here to help

Tappit adjustment is in the manual as is cam chain adjustment/setting.

You need to make a little tool as per diagram to release tension on the cam chain. There are marks then on cam shaft sprocket when rebuilding.

Worth taking off the bash plate and side front frame arms as a matter of course. You will need to support the bike via the back frame cross member or footrests to allow engine to drop slightly lower.

Careful when installing cam guides into bottom end of engine as can miss bottom locating lug.

Drain rad etc first.

All fully documented in engine rebuild section of the manual.

If you get stuck I'm sure there are enough people on here to help

thanks so much your very helpfull regards ste

hy sorry to be a pain what number page is the settings on in the manual cant seem to find them regards ste

06 manual

Page 3-5 valve clearance

Page 4-36 cam chain setting - reads a little confusing but I think it makes sense when bits are in your hands but if somebody can explain it better than the manual might help you.

Page 4-17 special tool to lock cam tensioner

Best of luck

best to take a lot of pictures when dismanteling

if you need to wait for parts you could forget something

manual is very good (i guess only trials bike with a decent manual)

work in a clean space and put your parts in little pots like they came of the bike

good luck its not so hard

best regards bob

thanks guys ill give it ago tommorow

hy all me again is it a big job to fully take engine out because im thinking of getting frame powder coated but i looked at bike today and it looks like a maze with all wires and pipes under fuel tank regards ste

Never stripped a Montesa fully but had head/barrel off and lots of other bits and at least Honda use correct plugs and colour coding so wires will only go back where they came from. It is a lttle congested under head stock area but so long as you remember where everything comes from should be ok. Pictures in manual give good clues on routing etc.

Basic mechanic skills, care and attention to detail, some photos and good organistion would normally suffice

thanks soo much jimmy for help regards ste

ive narrowed it down to a nocking piston

When you have the cylinder off, look very carefully at the front, top of the bore, about 5mm

below the top. With the "slipper" type pistons, a worn skirt will cause piston rock and often

wear the plating through on the "thrust side" of the cylinder. A very slight amount of piston

pin "offset" helps to keep this from happening, but a well worn piston can damage that area.

Jon