Dare I even say......

[TLRam1]

Since you guys like photos and seeing what's going on....I will post this for you to ponder over with some questions.

One of my vintage bikes Suzuki GT380.

The bike runs but was did not have the power off low end or top end. I checked compression they were 110, 105,110. Also had notable piston rattle.

Pulled the top end and here is what I have.

Scoring on middle piston. Is liquid suppose to be in the cavities in the crankcase around the pistons? Center piston rocks side to side, that's not good.



Heads, right being the cleaner side.



Bore is 54 mm stock and they all look like that with my inexpensive mic.







The top of the left piston has a protrusion on top with the center having an indention and the right having indention though less than the center. Is that the start of holing a piston??





This is the worst cylinder (center) the others look okay from a quick look. The center has some scoring.

Recommendations? Hone and new rings, bore and go oversize?

At what point do you know you have to go oversize and how far can you hone one Before having to go up?


I am pondering all of this before I proceed and seeing what's available for how much. Does this stuff ever end.

[Charles S Otwell]

I've seen this before, it's what happens when a chicken rides a bike too fast the cyclinders end up egg shaped  .. Sorry, I think your heartless humor is rubbing off on me

[dgc67]

Is liquid suppose to be in the cavities in the crankcase around the pistons?

Is that liquid oil?  If so, and this is an oil cooled engine, then yes.  If it is water/coolant in those spaces, or slight water/coolant- oil mix (some oil could contaminate the water/coolant during break down) and NOT a water cooled engine, then NO.

I would certainly replace the pistons/rings.  Feeling the inside of the cylinders do they feel smooth?  No waves, lines, ridges or obvious wear marks?  Depending on just how bad the scoring is I would just hone.  Another thing you could do it use feeler gauges to check the piston to cylinder wall clearances and make sure they are close enough to spec to only have to hone and get by with only slightly oversize rings to compensate.

Since you guys like photos and seeing what's going on....I will post this for you to ponder over with some questions.

One of my vintage bikes Suzuki GT380.

While I thorougly enjoy the technical aspects of this site, like this posting.  I really visit just to read about who is dating who, who beat up on who at last weekend's rally.  Interesting stuff like that!  Oh wait, that is the Desperate Desperado's Life website, my bad. 

[roboto65]

On the loss of power 2 strokes lose power when the cylinder heads overheat in this case head. Also the GT triples had a reputation for the middle piston seizing.  So it looks like you caught the problem before it happened as far as the oil well it is oil injected and might have alittle to much oil being injected in the fuel....  Hope I got some right  As far as what to do if the bores are OK I would do rings and pistons! If not well then time for bore and next piston size up..

[Greg Cothern]

Get the head magnafluxed and make sure its has no fractures etc.  Bore em up to the next size and new pistons and rings.  If your this far into it might as well do it ALL and the right way.

[TLRam1]

I failed to include the photo of the Center cylinder.

[roboto65]

I think it is time for a rebore Terry next size up for you!!!!

[Jester]

humor me on this but why do you say it's time to bore to next size?  TEACH MEEEEEEE... I think that's the saying 

[TLRam1]

The Center cage bearing came out this way. On the left is a good one.

[hootmon]

The Center cage bearing came out this way. On the left is a good one.

Terry - Tell me this is not in the middle of your Family Room... 

[TLRam1]

Is that liquid oil?  If so, and this is an oil cooled engine, then yes.  If it is water/coolant in those spaces, or slight water/coolant- oil mix (some oil could contaminate the water/coolant during break down) and NOT a water cooled engine, then NO.

This is an air cooled motor and the liquid should not be there. I believe and hope it was the base gasket and eliminated when I go back together

I would certainly replace the pistons/rings.  Feeling the inside of the cylinders do they feel smooth?  No waves, lines, ridges or obvious wear marks?  Depending on just how bad the scoring is I would just hone.  Another thing you could do it use feeler gauges to check the piston to cylinder wall clearances and make sure they are close enough to spec to only have to hone and get by with only slightly oversize rings to compensate.

There are scratches - score marks in the cylinder walls, not deep but maybe too deep for a hone job. I will have to take some measurements. As Charles mentioned the egg-shaped syndrome (Haha) service limit for the cylinder out of round is .0039" = .10mm and I don't have an instrument for that close of a tolerance for the cylinder.

With these motor you don't have oversized rings only you have to go to OS pistons also.

Desperate Desperado's Life website

You'll have to give this to me. 

If your this far into it might as well do it ALL and the right way.

Yep, I do want to do what's needed but no more monies than I have to spend. Hopefully I don't have to pull the crank for seals. I am thinking about this in parts and as a whole. These bikes are eating me up! I have 8 tires to put on, and need 2 more but it won't happen yet. If I have to bore and replace pistons and rings I'll do it, I want to measure a few points first to insure it's needed.

As far as what to do if the bores are OK I would do rings and pistons! If not well then time for bore and next piston size up..

I think you're on to something Allen!

humor me on this but why do you say it's time to bore to next size?  TEACH MEEEEEEE... I think that's the saying   

Jester, you might clarify your question some if I don't answer your question. Here goes, the difference or clearance between the bottom skirt of the piston and the cylinder wall has a tolerance in this case EDIT (I don't know, this info I need). If the distances are over that range you have to bore and move to the next size up in piston and rings to be with-in spec. Outside of the range will you have a good chance of lower compression and piston slapping against the cylinder wall gouging, scoring as you see now. It's also hard on the bearings as you can see the small end Rod bearing in the above post. Do you bore just because of scoring, not necessarily, depends on clearances. I was leaning towards the above posters to bore and move a half size up. I have not found the clearances but  want to measure first.

Either way I will be putting in new small end bearings, wrist pins, circlips on all three and the cylinders will at minimum be honed.

Also in a 2-stroke the crankshaft is separate than the crankcase oil, it's dry down there as in empty or should be. Injector oil is feed to the bearings than burned off so the crankshaft has rubber type seals to hold the charge air/fuel mixture from the carbs. If the seals are not holding your (normally 6 psi) your motor does not run properly. To replace seals the crank have to pulled and pulled apart, seals installed and pressed back together, trued, etc. 

Thanks for the great insight and recommendations, more to come.      

[TLRam1]

The Center cage bearing came out this way. On the left is a good one.

Terry - Tell me this is not in the middle of your Family Room... 

Nope, this one is in the garage! 

[TLRam1]

I had a couple of typo's and corrected for anyone who already read my post. Chgs are made in red.

[roboto65]

I found the owners manual in French LOL 54 mm  by 54 mm stroke square little thing HUH I am guessing you have no manual for this bike!!!

[TLRam1]

I found the owners manual in French LOL 54 mm  by 54 mm stroke square little thing HUH I am guessing you have no manual for this bike!!!

I didn't know YOU knew French, Bon Apetite!

I have a Clymer manual but it doesn't have THAT info in it or I need help locating it. It did have the other I posted previously. I am checking a few sources but nothing so far. Yep, 54X54, Charles could make a seat out of this.