Super Stuck Two Stroke Cylinder - 47yrs?

Introduction: Super Stuck Two Stroke Cylinder - 47yrs?

I've been attempting to 'Resto-Mod' a 1968 Suzuki T305 for a friend. for about 18months.

When I got it started it had much louder than the 'normal' two stroke rattle and ring, probably worn piston rings or cylinders which means the 'top end' has to come apart for inspection.

The right side was very tight to remove, one cylinder stud was stuck pretty good in the hole in cylinder

The cylinders probably haven't been removed since it was built in 1968.

The odometer reads almost 16,000 miles which many people will feel is very low but anyone with experience of 'high performance' two strokes will know is actually quite high miles for minimal servicing.

The service interval is variable depending on use, high rpm will wear things out much faster than mid range operation.

Step 1: The Offending Parts - Explanation With the 'easy' Cylinder

The problem is relatively easy to describe but the solution has been very difficult (and is still 'in progress)
The cylinders have holes through which are a relatively close fit on 8mm studs. As majority will know, aluminium likes to oxidise and form a white 'fluffy' coating. Unfortunately, when there isn't room for it to expand, it grips so tight onto 'stuff' it's almost welded. I kinda documented the steps so far in attempt to remove cylinder from crankcase WITHOUT DAMAGING ANYTHING

The first thing to do was the common, fill with release oil and wait 24 hrs. Well, I waited about 2 months (or more, Chris wasn't in too much of a rush) testing every day or so , not even the slightest movement. After 6 months it was getting ridiculous and frustrating.

Step 2: Measuing and Making - First Attempt

Took some measurements of cylinder and started making a 'core drill'

Had to modify a 7.8mm drill bit to get swarf clearance after hitting full depth, didn't quite work as expected

Step 3: Second Attempt

Drilled hole first, piloted with 3/16" 'aircraft drill then enlarged to final size. I didn't think even a new sharp cutter would work so made a holder for 4-1/2" angle grinder and ground outside to 8.4mm

Step 4: .........Check Your Material

first two core drills wouldn't harden, first I thought it could be decarburisation (?) -where the carbon in steel gets burned out of very thin sections

had to go for a third 'core drill', stainless steel just wasn't going to work instead of drill rod so made one out of an old swing arm bolt (couldn't find my 3/8" drill rod and didn't want to turn down 3/4"

Another failure, the section was so thin it folded in on itself (I only hardened tip as I didn't want to risk 'drill' snapping inside hole)

Step 5: Things Getting Serious

The clearance holes for the tube nuts holding head down are slightly under the tapping size for a 14x1mm tap.

With various parts and pices in the way, a tap handle can't be used but the square end of tap is very slightly larger than 10mm across flats and fits 'just nice' into a 10mm 12 point socket ( 4 sided tap fits into 12 point socket)

Step 6: Hydraulic?

Bolts made, holes tapped, add some grease to get hydraulic pressure down sides of studs. extra thin rule worked for adding grease and removing most of the air bubbles

Step 7: At Last, I'm Winning (maybe?)

Applied a bit of heat from propane torch, melted strap a bit more. Grease 'leaking' from between cylinder base and crankcase top, I know that stud isn't holding anything any longer and cylinder has actually moved about 1/2~1mm

Had to cut some board to fit under front of cylinder/exhaust port to apply more pressure

It's still 'WIP' but at least I know it will come apart without resorting to the final solution of drilling out 3 studs and finding (or making) new ones

So far this is a couple of hours a day for about 2 weeks.

When it's apart, the 'easy bit' Honing cylinders 1/2mm oversize for new pistons. which is next 'Instructable'

Step 8:

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    7 years ago on Introduction

    The Muriatic acid did a lot of fizzing but doesn't seem to have done any good to release cylinder. It has however, 'removed' most of the threads in holes. Probably have to step up to inch size or 16mm. I may just make a drill guide and drill out studs, (that is the final solution)


    7 years ago on Introduction

    Hi, I am an ex-zuke mechanic and have worked on these. Reset the base gasket and drop muriatic acid into the bores. suck out and repeat until it lets go. good luck and btw the carb slides are not the same on each side, so if you have removed them and put it back together and it runs funky, try switching the carb slides back. They look nearly identical but they aren't. I spent a lot of time figuring that one out. And you are right -16k is a ton of miles on one of these.


    Reply 7 years ago on Introduction

    Hi Tom, I was also in a Suzuki/BMW/Vespa/Yamaha dealer for a number of years, ended up running the workshops until 1990.(prior to that was at Honda/Yamaha dealers)

    I know about the carb slides, Yamaha did the same thing (we seemed to get a lot more Yam's with slides in wrong carbs) I never even thought about muriatic acid, I have some here from experimenting with DIY circuit boards (muriatic acid and Peroxide -works well) I'll be trying it later as one stud is still 'stuck' At least 3 let go though -LOL