Yet another SR250 Tracker UK Build

[JadusMotorcycleParts]

Great this project is on again!

The small bolt is your oil check bolt - that's why it's got the copper sealing washer.  It goes in the head on the spark plug side.

The larger bolt is the oil filter cover drain bolt - the lower of the three bolts that hold that cover in place.

[vortexracing]

Cheers Jadus



I think I have already installed the oil check bolt, is it the one that sits right next to a cylinder head bolt? its an M5 where as the small one in the photo looks like M4

It serves me right for not doing the bolt plating in bits. I dropped them all off with the platers and they all got mixed up.

Is the threaded hole in the head in the photo for some bikes that have a tacho fitted do you know? and as such nothing goes in there for my bike?


Hopefully engine will be fully built in a couple of weeks. Might try and source a new carb mounting rubber as the old one looks a bit rough.

Then its battery tray and seat next.

[JadusMotorcycleParts]

Correct with the oil check bolt in the head.  The only remaining one with a copper washer like that is the one on top of the oil filter cover - used to drain the oil from that cavity when changing oil filter.  This would make sense becuase your other mystery bolt was from the same part/location.

Yes, some of the later model SR's (even most from the Spanish factory) had a tacho drive off the cam shaft - meaning a hole in the head for that.  But it is not threaded, it just had a pressed in bearing then the cable has an oring on a plug with the wire running through it.

Yeah, double check the carb boot rubber - sucks to get an air leak there that only shows itself when the engine is warm - messing up all you carb setting work.

[vortexracing]

Cheers, after much Googling last night (and before you replied) I noticed the bolt in the oil filter cover   

So that's that mystery sorted, thanks for the help.

The hole in my head is threaded, its the one in the picture, just above the centreline of the cam. It is behind the top cam pulley, it looks like about an M5 thread.


My casting has the tacho take-off blanked off, ie not machined.

cheers

Dave

[C717]

Great thread to read, any update?

I've just signed up looking for advice and inspiration on an SR tracker I'm just planning. Do you have a list of part suppliers you've used so far? Quite hard to come by in the UK.

Currently toying with longer rear shocks and whether the mikuno vm32 carb is worth the swap!

[vortexracing]

not yet, just struggling with work and Christmas prep etc. Hopefully engine will be back together over Christmas

[vortexracing]

Right gents I need some help please??

Head is now assembled and finished

Untitled by eastham_david, on Flickr

Untitled by eastham_david, on Flickr

Untitled by eastham_david, on Flickr

Untitled by eastham_david, on Flickr

but embarrassingly I'm having trouble sorting the gasket/seal/spacer set-up for the head to cylinder and cylinder to crankcase.

I seem to have a plastic spacer too many in the gasket kit I bought (it's a full engine kit)

Does this cylinder to head seal/plastic spacer/metal spacer look right?

Untitled by eastham_david, on Flickr


and is the lower face of the cylinder to crankcase set-up right in this picture?

Untitled by eastham_david, on Flickr



and too finish, I'm still unaware of anything that fits into this threaded M5 or M6 hole in the head, is it surplus and only used for tacho off-take on some models?


Picture1 by eastham_david, on Flickr


Thanks in advance

[JadusMotorcycleParts]

You are correct on the tapped hole in the head.  It is only used on the models with a tach drive there.

I am 90% sure you have the orings/gaskets/dowels wrong on the head and the barrel.  I couldn't find my reference photos right this minute but check these exploded diagrams to be sure:  https://www.cmsnl.com/yamaha-sr250t-1981-exciter1-usa_model8812/partslist/A-06.html#results

[vortexracing]

Cheers,

I'm sure the red O ring and thin metal sleeve sits in the oil way on the crankcase

i.e. the top right position here

Untitled by eastham_david, on Flickr

This coincides with the same position on the lower cylinder in this picture

Untitled by eastham_david, on Flickr

The other plastic sleeve and metal sleeves in the upper face of the cylinder/lower face of the head look like this with he gasket in place

Untitled by eastham_david, on Flickr

The rebate/counter bore in the right hand upper corner of the above picture is quite deep and I'm sure that's where the plastic spacer sits. The picture below shows how deep that counter bore is, this is also the oil way so that's why I thought these had spate seal to the other 3 x head/cylinder bolt holes. 

Untitled by eastham_david, on Flickr


cheers for the advice and help, heaven knows I need it.   

(two strokes are so much easier)

I have had a look at the cylinder diagram (thanks for the link that helps a lot) and the equivalent head diagram and the seals/gaskets appear right, but I could be wrong.

Dave

[vortexracing]

Just about to pop new rings in and checked the sizes of the old rings, they are mainly gapped at 0.65mm ish. Took the new rings out of the packet and placed them in the bore only to find they overlap 5mm, is this correct. In my old karting/2 stroke days they rings only needed a small fettle if anything, these appear massive.

I have checked the part number and the bore size (73.5mm) and they match. Surely you shouldn't have to try and trim 5mm off them

if that is the case, how the hell do I do the oil control ring. I'm hoping they are just the wrong rings.

any help would be much appreciated

Ta
Dave

Untitled by eastham_david, on Flickr