Stihl conversion project: MTX.45 + 051 = 076

OK, so I'm getting round to doing this. I bought a Stihl MTX.45 rail saw off ebay. I assume it's an 076 in hiding because of the decomp valve in the RH hole. It runs good, well starts and idles fine. Doesn't rev up high at all, I've never used an 051/076 before - is this the carb governor cutting in? It's made in Brazil... what's the quality like c.f. German? It has a nasty DIY paint job, but otherwise feels pretty good.

I've also got this non-running (no spark) 051. I was hoping to put the oiler gear in the rail saw and instantly have an 076 (- manual oiler), but I think I've just found this won't be so. I'd need to split the crankcase to put the oil pickup in, at the moment it's a second fuel tank (a pick up line feeds into the top of the main fuel tank). I'd rather not split the crankcase (haven't done before, hear it's a pain).

So I'm planning on swapping the jugs/studs over. I'm pretty sure the 051 oiler works - all gears look fine and there was oil all over the bar when I got it. Shall I throw a new set of rings in while I'm at it, or assess when I get it apart? What are the cylinder studs like to remove? I'll also swap the flywheel, ignition and starter cover.

Would a crankcase split be easier than a cylinder swap (although I have successfully done the latter on my 056)? Can you get manual oiler assemblies? I've got a new clutch drum + rim sprokcet coming, you can see the old drum+pully set up on the rail saw now.

Anyone got any comments/advice?


MTX.45


MTX.45 pully etc.


051AVE


051AVE sprocket etc.


MTX.45 second fuel tank/oil tank pickup - can see blank where oil pickup would mount


051AVE showing oil pickup - no getting in there without a crankcase split

well my good spirits are short lived...
The piston is totally rooted, the cylinder isn't much better. This is a real pain, but it serves me right for assuming the P&C of a 2nd hand cut-off saw would be in perfect nick. So I guess I've got a few options, can some of you input here...
1 - Buy a brand new Stihl P&C - EXPENSIVE!
2 - Give the cylinder a hone, get a Stihl piston & rings - not so expensive
3 - Give the cylinder a hone, get an aftermarkt piston & rings - even less expensive
4 - hang around for a good 2nd hand P&C to turn up
5 - Pull the 051 down now and if it's good mill with it instead

After initial depression, I'm leaning towards a combo between 3 and 4. I know some may not approve of aftermarket pistons etc., but I need to get milling soon (furnishing my new house). It started and ran nicely in its current state, (compression did feel a bit low but) so surely with a light hone and new piston/rings it'd be a whole heap better? The scoring is only just feelable with the fingers in one spot, the rest feels good. I'll keep a look out for a good cylinder in the mean time though. And if it's really gutless I'll just have to change tactics.

So, does anyone know of a good 076/075 P&C, or just cylinder I could get?

I guess it was foolish not taking this into account before, and what I've ended up buying for sure is a working ignition system, a solid body and a grinder attachment for a large mount Stihl. I guess £50 could get you less...


scoring


more scoring


nice...


there was nasty gritty deposits at the top of the clyinder, gotta be the cause of the cylinder scoring. But what about this piston damage?

What's the approved way of removing the cylinder studs? Vice grips on the middle of the shaft? I don't have a torch here to heat the crankcase. Are they M6 on the bottom, or just the top - as in, will I need to tap the 051 crankcase out to M6 (having M5 bolt holes normally)?

What's the approved way of removing the cylinder studs? Vice grips on the middle of the shaft?

Click to expand...

Screw two nuts onto a stud. Tighten them onto each other - they will lock. You can then undo the stud using a spanner on the lower nut. Vice grips? Ewwww!

Bad luck on the P&C. I have learned to price in at least a new piston on a second hand grinder - they lead a hard life and are usually screwed. Cylinder looks recoverable if that is piston material transferred on, rather than cylinder material ground out. What is the diameter?

rxe said:

Screw two nuts onto a stud. Tighten them onto each other - they will lock. You can then undo the stud using a spanner on the lower nut. Vice grips? Ewwww!

Bad luck on the P&C. I have learned to price in at least a new piston on a second hand grinder - they lead a hard life and are usually screwed. Cylinder looks recoverable if that is piston material transferred on, rather than cylinder material ground out. What is the diameter?

Click to expand...

ah yes, should have thought of that, good idea. To be honest I can't tell if it's piston material on the bore, it could be looking at the amount lost on the piston. How can I tell? I guess it'll come out in the wash when I use the brake cylinder hone.

Diameter - you mean nominal bore (58mm)? Or ring end gap? Rings are screwed defo! I'll wait till I get new ones. So do you know if I'll have to tap M6 threads in the casing?

I often see posts here about "muriatic acid" for cleaning bores - I have no idea what this translates to in UK terms - probably sulphuric acid which would burn off the aluminium and ignore the chrome.

I asked the bore question because I'm getting a flex hone for the 070 project - I'll let you know how it goes and you can borrow it (where in the UK are you?) if it works for me.

Based on the 070 experience, the stud threads will be M6 already - I wouldn't like to try and tap a crankcase unless I had a proper machine shop at my disposal.

Edit - what is that big notch in the bore on the rhs of your "more scoring" picture?

rxe said:

Edit - what is that big notch in the bore on the rhs of your "more scoring" picture?

Click to expand...

I think you're looking at the thread for the decomp valve.

Hi,
I'm from the UK as well (if you count Cornwall). Muratic Acid is Hydrochloric Acid over here. I've got a 064 cylinder which I am going to try to clean up with it when I can get hold of some. It seems that some path cleaners have HCl in them but could someone give an idea of what strength is needed? By the way that looks like a TS350 filter setup on top of your saw.

yeah, nothc his the decomp valve thread. I'll look at HCL acid - maybe I'll hone first to see itf it's taking any off. Although, I'd love to have a go with your flexi hone rxe, right now I'm in Bristol...

The IPL and manual say the cylinder bolts on the 051 are M5, the studs are M6 on the 076. It doesn't say what the bottom of the studs are. I guess I'll just pull them out and see. But I don't see any other option apart from tapping new threads if they are M6 on the bottom though...

my bro's in the chem department, I'll try and get him to aquire tome hydrochloric acid. it sounds good, do you soak ot? It may be a ts350 filter - it is a cut off saw. But it will soon be using an 052/076 one!

the crank case is a different part no for the 076 and 051, I assume because of these threads. So I tap new holes or split the crankcase. What's invoved with splitting the crankcase? Will I need to heat it to remove the bearings? Do I need a special tool? Still thinking tapping sounds easier


the stud hole has an open back - where does this lead to? It doesn't seem to be part of the crank chamber, is it just an empty casting space? I ask this because I want to know if I can let shavings (from drilling and tapping) fall down in there?

They're actually blank, I was wrong, no worries I'll use a plug tap to finish.

On another note - has anyone had their clyinder recoated with nikasil, like they do with bikes, http://www.dpsracing.co.uk/barrel_repairs.php?osCsid=555fb18348e8f7e385e94435ce7aa9e6
It may not quite be worth it, but it's cheaper than an OEM one... Any reason it wouldn't be good?

You need a service manual.... .

Lakeside53 said:

You need a service manual.... .

Click to expand...

I have one, sorry should have read it more - according to it I have a chrome plated cylinder. It says if you have a piston without a circle round the size number you need to use a chrome plated bore, but if I had a different piston (which I will), would nikasil be ok if I had a psiton with a circle? Is nikasil inferior then?

That info is way out of date.... remember, that manual was likely written 25 years ago. Just use any piston you get. Some on this site will tell you that Nikersil is way better the chrome, but.. not all chrome is created equal. Some chrome is cheap and worthless, but on Stihl saws it stood the test of time on many models.


Also, if that manual says to use a soldering iron to heat the inner race of the bearings - don't.... bad advise for todays bearings, and hard on any bearings.