XS2 - Cam chain slipped - Adjuster not the correct type - can of worms !

[Flyingspanner]

I have just started bringing my stored XS2 back to life for the summer - I am going to fit an Electronic TCI so decided to check the cam chain adjustment, valve clearance and riming, I removed my Acorn nut from the adjuster and the pin was sticking out maybe 10mm - no matter what I did I could not get it flush, it always came in and out - my mistake was to turn the bike over on the starter with the adjuster too slack and the timing chain appears to have slipped a tooth as it’s way out of line and, so it looks like the chain needs to be replaced and set correctly, (I need to do the vale seals anyway) so engine is coming out, thanks to a great post from 5twins on adjusters mine should have been a type B - but it is a 6 hole plate and seems to be a type E by the measurement, but no locknut or rubber washer fitted ? - I decided to start listing the required replacement parts, seal kits, sealant, chain and master link etc, and as a double check on my engine I decided to cross reference the engine S/N with the lists of model years to confirm and this is where it gets strange the engine number stamped on the case is 2FO-159947 which is listed as a 78/79 XS-SE not a XS2 engine !! - but the rest of the engine seems to be correct for a XS2 - lever electric start and decompressor, not electronic ignition, BS38mm carbs ??

Any ideas what I actually have and what series would I use to order the correct chain, gaskets oil filters etc

Thanks for any help offered

Bike was an import from the USA

Andy (UK)

XS-SE (us)	77-78	2MO	2FO- 100101 to (150000)
XS-SF (US)	78-79	2M0	2FO- 150101 to (200000)
XS-SE (Can, Other)	77-78	2M1	447- 900101 to (910000)
XS-SF (Can, Oceania, Other)	78-79	2M1	447- 910101 to (920000)

 

[Its been a long time]

Perfectly possible you have a later engine in an earlier bike. Engine number is pretty definitive.

 

[Flyingspanner]

Perfectly possible you have a later engine in an earlier bike. Engine number is pretty definitive.

Yes I think it’s looking like that - a previous owner has replaced the engine and must have transferred the rocker arms so the decomp works - I guess this means I need to order engine parts for the 78/79 SF now

 

[Its been a long time]

Yes I think it’s looking like that - a previous owner has replaced the engine and must have transferred the rocker arms so the decomp works - I guess this means I need to order engine parts for the 78/79 SF now

You need to have a good look at the carburettors that are fitted. So that in the future you get the correct parts when you need them. If needs be, post pictures here so that the resident experts can advise you what you have.

 

[Flyingspanner]

Will do - I had the carbs fully rebuilt last year - they are Mikuni BS38

 

[Its been a long time]

Will do - I had the carbs fully rebuilt last year - they are Mikuni BS38

OK. They're early carbs, so most likely they're XS2 spec. 78/79 bikes also had BS38s but set up differently. That's why I asked.

 

[Wingedwheel]

When you pull the head count the teeth on the cam sprocket. There was a change 74 forward.

 

[Flyingspanner]

Quick update - cam has 36 teeth and the chain is very slack - I have now taken the engine out and have found the fwd guide has totally lost its black plastic, it has disbonded from the guide and was just sitting there, the chain had also started to rub against the metal of the guide !! - so good job I stripped the engine down

 

[Flyingspanner]

So after stripping the top end down, I found the pistons are +0.50 oversize, the pistons do show signs of wear and some form of black marking / pitting ?? - the barrels are great no scratches, ridges or damage. I did the feeler gauge check with the rings removed and could get a 0.004 in with the piston 1/2” down from the top, and at the bottom of the barrel it’s 0.003” - so looks like its worn and slightly tapered, putting the rings in the bores and the gaps are way out of tolerance as well - so looks like a rebore and new pistons is needed

 

[Flyingspanner]

Con rods have 447 stamped on them and the pistons size corresponds to the dimensions I have seen for a 447 so I will need to buy a 0.100 full set - unfortunately I can’t find any in the UK but have found some with Cruizimage in Japan - I have sent him a msg to see if he will ship to the uk - I did a search and it seems a few guys on hear have used his pistons - on disassembly I found the head gasket was copper - is this the best one to use ? Or is the one with the Vertex gasket kit ok as I can’t buy the copper one in the UK - thanks all

 

[Its been a long time]

IMD not have any in the UK? https://imdpistons.com/

Several members have used Cruzin Image. Seems a good option.

 

[Flyingspanner]

IMD not have any in the UK? https://imdpistons.com/

Several members have used Cruzin Image. Seems a good option.

I have looked and the don’t show any +1.00 for the 447 engine they do have the 533 version - have sent them a email to see if they can help

 

[Jan_P]

Last time I checked rebore and new pistons was expensive and buying a set cylinders and pistons was an alternative.
I believe Cruizin image have those but also other.sellers

 

[Its been a long time]

Also it's possible to resleeve the barrels if you want to go standard size again. In the UK, these guys are respected cylinder liner manufacturers. https://westwoodcylinderliners.co.uk/

 

[Flyingspanner]

Last time I checked rebore and new pistons was expensive and buying a set cylinders and pistons was an alternative.
I believe Cruizin image have those but also other.sellers

I may look at this option - I even thought about going big bore

 

[Flyingspanner]

Also it's possible to resleeve the barrels if you want to go standard size again. In the UK, these guys are respected cylinder liner manufacturers. https://westwoodcylinderliners.co.uk/

Thanks - will take a look as well

 

[Jim]

I even thought about going big bore

That's how I'd play it. You're gonna spend money on pistons and jugs regardless. Going big bore would prolly be close to a wash moneywise, and a big boost in performance.

 

[650Skull]

I may look at this option - I even thought about going big bore

Last time I looked a few days ago they had 2mm 447 oversized pistons kits.

That's about 687cc. Also leaves room for another oversize bore to 706cc without resleving.

 

[Flyingspanner]

Tried all the UK and EU options no stock for the +1.00mm - so have bought a set from cruzinimage.net - he is shipping to me this week - when I take them to the machine shop for a be rebore and hone to fit the new pistons, I will tell them 0.002” clearance total - so 0.001” each side - is this correct ?
Thanks

 

[Its been a long time]

Tried all the UK and EU options no stock for the +1.00mm - so have bought a set from cruzinimage.net - he is shipping to me this week - when I take them to the machine shop for a be rebore and hone to fit the new pistons, I will tell them 0.002” clearance total - so 0.001” each side - is this correct ?
Thanks

Sounds great. Keep us posted.

Did you order on their website? I found I can't create an account on Cruzin Image website.