XT600E 1991 Ex Aust Army Project

[Danjet600]

getting stuck into the motor rebuild today, started by building a engine stand
raided the scrap metal bin and

mounted up ready to crack it open

had to relocate the work bench lots more room to move now

this motor seems to be in good nick


the piston on the left is from the army bike, the right is from the motor i bought in pieces for the 3aj

little end has got wear and what looks like a hot spot

the bore in the barrel is ok will still be bored out to the next size piston

strange mark on the bore no edges or lip to feel

$70 to get the barrel bored out so i thought i'd get them both done

[ActionManMelb]

Hi Dan, just some advice drawn from my 30+ years rebuilding engines and transmissions. Many people rebore at the drop of a hat when a hone and a new set of rings would give you another 25,000-40,000kms at very little cost. Lets face it, at our age we are not going to be clocking up huge distances.

If you cant feel any irregularity in the bore, then I would advise a hone and inspect before boring and new piston.
The army piston and bore looks mint from my loungeroom.

The BRM hones are the bee's knees for this job. Commonly referred to as a dunnybrush hone.

[Mezo]

Id say that mark was a rust spot where the piston had been sitting for a while Danny

Mezo.

[Danjet600]

took the barrels in to be bored, price drop to $60 ea had the bore for the army bike checked has a 4 thou gap between the piston and bore bloke said was a bit iffy said should be 2.2 thou, well i think thats what he said? so i went with the next size up and lashed out on a weisco piston

[Mezo]

Interested to know the price Danny

Mezo.

[ActionManMelb]

has a 4 thou gap between the piston and bore bloke said was a bit iffy said should be 2.2 thou,

That what happens when you take a boring problem to a bloke who MAKES money from boring things.
Brand new spec is 2.2 thou, wear limit is 4.5 thou.
This spec is quite tight compared to many other bikes, especially considering the large bore size of the 600 single.
My BSA 441 spec is 5 thou new, wear limit of 8 thou.

I still reckon you could have honed it and put some new rings in (gapped to 12 thou) and saved yourself enough for a half a dozen slabs of creamy, foaming, ice cold BEER.

[Danjet600]

Interested to know the price Danny

Mezo.

$220 for the piston and bore for the 3aj , i just thought fuck it, do it, do it properly

the small 2.2thou gap is small compared to other bikes is this why when the rings wear the piston skirts scrape on the bore?

[rywong]

Id say that mark was a rust spot where the piston had been sitting for a while Danny

Mezo.

I agree mezo,
I know that some of those army bikes would sit for years with the only work being a test ride when they got their
6 monthly service.
7 CSSB at Enoggera had 12 XT's and only 2 got any real work.
The others would still get a complete service every 6 months (army regs).
Some even got rust in the bore from sitting so long.

[rywong]

Did you get the ARMY service/log books with the bike?
They were very detailed.

[Danjet600]

Did you get the ARMY service/log books with the bike?
They were very detailed.

no didn't get any log book for the bike, got a good list of bits that the previous owner and mike had done, it's a shame the log books would have been good to keep, might have upped the resale value down the track
as far as i know these bikes go to auction as is just the luck of the draw