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XR80 piston replacement

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Hello all

Last year I bought my young sons a pair of XRs an 80 and an 100.

Being too protective I did not instruct the boys on how to shift...

and of course the hottest day of the year is when we went out.

The 80 seized up, and I got her broke free but now i need to replace piston, rings and hone.

I have worked on my other machines...

I did order a manual, it states it is a Honda shop manual, but looking through it I am not sure..

I was under the impression that with an overhead cam, you need to put the motor into a specific time, prior to removing the head and the parts under...


Bonus question is...

since I will already be inside the 80, can I get her to 100cc or close?

I do aprreciate my sons battling for something, but it does get old after a bit




thank you for reading and looking forward to your advice



Edited by fritzl65

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Who published the manual, what is the title. Can you

post a photo of the cover?

Genuine Factory Service Manuals for all current and many

older models of Hondas are available from HelmInc.com.

The XR80 & 100 are single overhead cam engines. While

positioning the rotating assembly such that the piston is on

the compression stroke and both valves are closed might

be of some small benefit during disassembly, IMO, this does

not matter. Let's see whether others voice dissent.

OTOH, it WILL BE ESSENTIAL during reassembly to ensure

that the camshaft and crankshaft are correctly oriented/timed

to each other. The procedure for this will be described in the

section detailing installation of the timing chain.

Big displacement kits are available for XR80s. Under the

personal circumstances you have described, my suggestion

is that this repair be limited to the first overbore that will

enable the cylinder walls to be cleaned up. Just get the bike

working again in a stock (aka trouble-free) configuration.

Then the sons and you can go through the learning process

for riding AND OPERATION/MAINTENANCE of a motorcycle.

In due course, replace the bike with a bigger one.

To put this bluntly - the family managed to seize what is

NORMALLY a pretty bullet-proof stock engine - APPARENTLY

on your first outing with the bike. In such circumstances, a

modified engine is likely to prove to be an expensive headache,

the bike it is in has a good chance of soon being discarded.

Increasing the displacement from 80cc to 100, 120 or beyond

requires more than just an increase in piston/bore to be successful.

Carburetion, exhaust, valves, ignition and cooling may all need attention,

too. Also, once modified, it is not unusual for such engines to require

more frequent maintenance and other attention that a stock engine

does not need. Blowing up the stocker does not bode well for a happy

coexistance with a poked/stroked replacement.

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The boys and i trmived the motor from the fram an then tore into the top end. We did not cook the motor in the sun. The tappet adjuster came loose and went between a gear and the timing chain

Cant figure out how to post pictures via my phone

So now i think i am going to have to split the cases to replace the timing chain.

Or is there a trick?

Maybe a master link chain exists?

Maybe i could open the timing chain and reple it and relink the chain?

Thanks for reading


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So we tore into the XR80R

I cracked the tight nuts and bolts...

the boys removed them. I have the manual on a cd, which is now loaded on the all in one pc which is the garage manual depository..

The manual is easy peasy...

go to chapter 7 for cylinder removal...

it states:

step 1 remove seat see section 3-2

step 2 remove side cover see section 5_6

and so on until the engine is removed


the boys kept at it between the manual and me telling them to bag and tag everything we got the motor on the bench and the top off


As you can see one tappet adjuster is missing. The motor did not get overheated and seize as i thought. The seized sensation was the adjuster in between the chain and the gear. What I thought me breaking a seized pistion free was me actually snapping this little timing chain.


sorry for double posting this...i am still getting used to the search function here...

i have read some contradictory posts about replacing this timing chain...

split the case and its not necessary...

can someone with practical experience help here?

this is a 2002 xr80r..

thank you for reading


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I forgot to mention the manual we are using is the Honda issued May 1999

Honda 1998-2003 XR80 XR100 Service manual.



Today, using an impact screwdriver and a micro torch, i removed the stator/ignition assembly.

Can I remove the crank seal and slip the chain in?

Has anyone done this on the 2002 XR80?

Or will I have to split the cases and remove the crank shaft

Thanks for reading

Edited by fritzl65

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I have not done it but others have written about

extracting and replacing the timing chain through

the opening created when the left crank seal is


Since the focus of the work is no longer piston

replacement, perhaps consider starting a new

thread with a title referencing timing chain replacement

for better replies from people with experience.

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