Cylinder Work?

[viclioce]

I have a Model 95 cylinder which I pulled off the bike. It had a .04 piston and rings in it when the top ring cracked. What I want to know is do I get this bored bigger? Do I send it to a shop to have the cylinder wall reconditioned to a smaller over size or is it more cost effective to find a .01 or .02 cylinder and matched piston and go from there?

This is the next evolution in the Model 03 with a Model 94 bottom end, a Model 95 top end and the Model 93, 24mm carb. I'm thinking I will update the cylinder, match a piston to it, go with the standard Model 95 piston/ring combo and buy a bigger carb. This will make it more like an original Model 95, performance wise. At least that's the hope. I'm in no rush because It's powerful enough for my grandson to learn on for now. But when he gets tired of it (I know he will!) then I will do the upgrades. I don't think at this point I want to go to a reed valve config and piston. That may be something way down the line.

In fact, I will most likely go for a larger off road bike, in the two stroke category, before considering upgrading the Wombat to a reed valve system. ; D Victor

[olddogs]

If you are currently at +40, they sell a +50 Wiseco piston right on this site. Most machine shops will be able to bore the cylinder to fit the new piston. Make sure you specify what clearance you want and remind them to chamfer the ports when done. The cost of the new piston, rings and gaskets are comparable to what a good used model 95 cylinder and matching piston would cost, if you could find them, in usable shape. You will also find that a lot of the existing Combat cylinders have already been modified to reed valve.

[Zyx]

The cylinder mods you speak of will restore the cylinder to use, but whether it is more powerful than what you have may be a matter of small degrees unless you convert to reed. That one change alone will make a world of difference in response and pulling ability. The 95 porting isn't all that radical. I will take a look as compared to the 03. As for bigger carb, up to a point that's a good idea, but without the reeds, you will find a point of diminishing returns when going bigger on the carb. If you want to stay piston ported, you will need to port the cylinder to get full use of a larger carb, and at that point you will be giving away bottom end, and probably need a tuned exhaust. The one you have is technically a tuned system, but is mild and aimed at the original build. Changing just any one of several things generally won't do much, and sometimes will make things worse.

Start by deciding how you want to ride this bike. Where is the power now and where does it need to be? How much more power sounds right? Do you want it to be as rideable as it is now, or are you looking for something more aggressive? If all you are looking for is, essentially, a combat motor in an 03 frame, stay with combat parts and possibly the pipe from a combat.

Larger overbore will add a smidge of power, but you will need to use a Wiseco piston and rings. That may mean you can't fully utilize the boost port on the combat cylinder, and you will end up with something more like a 94 than a 95. This was discussed just recently in another thread.

Personally, if you want more power and keep ridability, I would do the reed conversion first, and then use a larger carb, and so as to use original style combat pistons, have the cylinder plated back to stock dimension. I haven't checked cost lately, but you should be able to do that for about half the cost of a new cylinder.

[viclioce]

How would I know if the cylinder has been modified for Reed valve? I'm not at all familiar with that configureation. I know the piston needs the additional holes in the bottom to let the air mixture through. All I know is both the cylinders I have now have Victory Ports, the big V's which are not in the 94 and 03 model cylinders, right? Are there additional transfer ports or other ports in the cylinder for the Reed valve configuration?

And I figured a 28mm carb was stock for the Model 95 CW so I thought this model 93 24mm carb was a bit under sized for what the Model 95 top end was used to having, right? The current carb has a nasty habit of getting sticky. The slide and its corresponding wall get so sticky after awhile that I have to clean both with 2000 grit sand paper and carb cleaner to keep the paper wet. It did it again to me yesterday and I'm getting tired of having to treat the carb slide, so I figured if I buy a new carb, I would go with a 28 mm since that was what the model 95 cylinder ran with stock. Thanks! ; D Victor

[Bullfrog]

Whatever is making your existing carb sticky will make a new carb sticky. Let's find the source of the "sticky" problem. Whatever it is, it is also going into your engine - and that's not good.

What is the condition of your air cleaner element?

No one else's carb is getting sticky requiring regular scrubs with carb cleaner, what is strange about your intake system that might be causing that?

Ed

[Zyx]

You are correct that the CW used a 28. My error. Conversion to reeds would require a reed block that mates to the cylinder stud pattern, and accepts a two stud carb with the right bolt spacing, or a spigot and spigot mount carb such as used on the 98. It's been done. My point is still that the differences between the 03 and the 95 are slight, and I would favor the 03 because it is a running combination. I recently went out of my way to buy an 03 cylinder as a woods engine top end for my 97 bottom end because all the 98 gear bolts up, and I have that laying handy. The extra two mm in exhaust port height in the 95 won't add a lot on its own. The opinions of others may vary.

I agree that something is causing your slide to stick. I have a carb that hasn't been cleaned or overhauled since 1974 and it doesn't stick. I don't think I have ever had one that did, or ever treated the issue as a mechanic for Honda and Yamaha. Are you still using bean oil? When it sticks is the slide clean or gummed? You should never have to sand on a slide. Certainly not repeatedly. Sounds like oil residue is causing it to stick, and regular two stroke oil won't do that. Bean oil might. If it stick again, try cleaning the slide with alcohol. If that frees it, it is oil gum.

[racerclam]

vicloice

I may hve the reeds you need and if not I have the factory reeds used in the 97 98 03 and toads . I ave addapted several to use these reeds with the wider stud pattern by plugging and re drilling them , at that point you can use a spigot mount 32mm or 34mm carb which is a better carb setup.

Rich