Cylinder question from a Gp newbie

I would like to thank those who answered my questions on rebuilding, tuning, and other little things. Talking to you Gp guys I'm not to worried about changing pistons, tuning, and Changing the crank. But now something came to me. Wait a min all of these rebuilds, How many times can you reuse a cylinder? I've heard people talking about replating. I guess that is that cylinder coating? Can you just resleeve them? I've checked prices and a cylinder is more expensive than the case set?

 

Most of the people I have spoken with on the replating subject say "don't do it". The feeling is that the plating comes off too easily.

I have no first hand experience with replating so I'm only repeating what I have heard.

For what it's worth...

Monty

 

I just replated my KX. I HOPE it holds up. Looks good and everything fit right, at least. Cylinders last a LOOONG time, unless you stick the thing and tear the nickacil. That's why I had to replate the KX. That nickle-chrome is hard as hell, wears a long, long time before ever wearing out.

DON'T sleeve the thing. Now, my experience with this was with an old parallel twin TZ250. It had sleeved cylinders when I got it. First place, steel isn't as hard as nickacil, but that's not the main problem. The liner doesn't conduct heat as well away from the piston and to the water jacket and most importantly has different thermal expansion properties. The pistons are not designed to expand into a hot steel liner and I had seizure problems, couldn't make it work. I set the thing up loose as I dared and it still wouldn't work, so I gave up and bought a new set of cylinders and didn't have problem one after that. Stuck it one time after that at Daytona and that was a jetting problem, not the cylinders.

Jack

 

So don't worry about it. I'm just wondering why you guys might have spare cylinders and how often you need to gotto the spare.

As far as I can tell worry about pistons, rings and cranks, and change them after so many miles.

Don't worry about the cylinders it takes forever for them to wear??

 

Cylinders can last along time if you watch your jetting and keep the engine from sticking a piston real bad. If you do stick a piston most times it is not terminal to the cylinder. We use Miriatic (sp) acid and a Q-tip. Just put a little on the aluminum that is stuck to the cylinder from the piston. Wipe clean and wash. Inspect for damage. Normally a scratch below the ring line will not hurt anything in the future. If it is above the rings your screwed. The standard rule is if you can catch you finger nail in the scratch it is to big.

As far as replating I don't do it. Never had to really. I had my Yamaha for 2.5 years and it was on the original cylinder. I had a new spare and never put it on. I only scuffed one piston and it wasnt anything to worry about and didnt do any damage. If replating is what you want to do and many people do I would send the cylinder to MCE. The problem with replating them is that the platers many times do not cut the port edges correctly or not enough. There is a recess on the Honda for the exhaust bridge that has to be just right. Also they usually come back shorter than when they started. This can run into squish problems. Having Kevin check it out when it comes back is a really good idea. He usually only charges for any post work that needs to be done and will not mark up the replating. Check with him this may have changed.

There is nothing like a brand new cylinder but as you said they are costly...

Bill Cole

 

Yeah, I had a nick just above the exhaust port on the KX. If it wasn't for that one little nick, I'd have been okay. Still, I cleaned it up with muratic (actually 37% HCl) acid like Bill says and threw everything back together with an old piston and rings I had for a spare and it ran a two hour endurance and sprint the next day without problems, though down a bit on power due to the different piston, stock rather than Wiseco with a slightly higher dome/more compression. The compression had been set with that Wiseco. When I got home, I shipped the cylinder off for plating and ordered a new Wiseco piston kit.

So, even a cylinder with a bad nick can work for the rest of a race weekend. I don't have a spare for the RS, didn't have a spare for the TZ.

Jack

 

Thanks you guys. Looks like I will be riding Gp125 next year, so called weed-wacker pilot by those who ride bigger bikes. Bill and Jack I was wondering if you guys may have any notes on jetting TZ's, Temp, humidity and what jet you used. You guys are like TZ gurus. I have never done it and will be gp grasshoper next year.

 

Bill's the guru, LOL. I don't take a lot of notes and sort of jet by ear, probably not the way to go about it on a professional level, but it's just the way I've always done it. Perhaps Bill can help. I don't have a barometer, air density gauge, etc. Most of my racing is don't only at a few tracks. If I were running all around the country running everything from Pike's Peak to No Problem, I'd probably have to invest in something and start taking weekend set up notes. But, if I have a question, I always just ask one of the high dollar guys around what they're doing with jets. Then I go with what I know will be way rich by probably two or three mains and work my way down by plug cuts. It's not that big a deal for me, though, because I know what works at TWS in cool air and warm air and I jet accordingly. TWS is where I run the most and it's not far off from other Texas tracks. When I do track days at Hitchcock, the air is a little denser, lower elevation, and I jet accordingly. And, NPR is really dense, damned near below sea level. Sometimes at a track like TWS that I run all the time, I don't even have to mess with jetting beyond taking a plug cut just to check. I stick what I know will be needed in the carb before leaving. I usually run a jet on the rich side.

You'll have to learn to read plugs. Probably best to seek out a mentor for that til you get aquainted with what you're looking at. When I was AMA racing, there was this plug guy, worked for Champion. You'd take your plug to him and he'd read it like a friggin' book. I learned a lot from that guy, but I'll never be that good. My eyes are getting worse in my old age. Probably ought to invest in a hand lens.

Bill's probably got notes and density guage and such, That's the way it OUGHT to be done, I suppose.

 

As far as replating (TZ-250), never had a problem. I use Millennium Technologies. [Running ported and replated cylinders now.] Never used MCE so I cannot comment directly, but hear alot of good things about them.

Biggest thing for cylinders is to monitor bore wear. When you do send it out for replate, be "specific" as to what you want in sizing and verify all work. (I think too many people throw them in a box, mail them off, then install them when they get them without any measurments, and then wonder why they have problems)

Never ran into any problems squish problems, but thats what different base gaskets are for if you do...

Hope this confuses you even more

 

Well what I can tell you is that you do need to run the yamaha a little lean on the nozzle to make it carb. clean. This is usually a problem when guys are starting out with a Yamaha. When you close the throttle, many do when starting, the engine runs into a rich condition. When you open the throttle it will buck and as we call it Gank. If so drop your nozzle one size.

It is hard to give jetting info as many factors effect jetting. I can give you my set up and you can judge from there. My engine was a stock 95 with stock 95 cylinder. I ran 2.3mm of timing all the time. I ran Sunoco standard fuel (purple) and A-747 at 30:1. My baseline carb settings were 360 main, R-6 nozzle, 17.5 pilot, air screw +2 turns and 60 power jet.

You only need to change the power jet at Daytona so leave that in. Within the parameters above I would only stray a little. If it were cold 50-65 deg. in the AM I would go to the 370-380 main and maybe a 20 pilot jet. If it got hot 90+ I would go to the 350 main with a 15 pilot and if the air was real thin I would run the R-5 nozzle.

When I was learning to ride I did start with the R-5 nozzle. Don't be scared to put it in. It is rare that you can seize on the nozzle setting. You will also run that in the rain as the bike will run rich from so much closed throttle.

I also installed a 4.0 slide and would run that in the mid summer and put the richer 3.5 slide in during the spring and fall.

Best thing you can do is to pick a fuel and oil and stay with it. This way you can learn your jetting from that fuel. Many jet the same but many are way off. For example I ran 3 sizes leaner on Sunoco maximal than on standard. If you start on Maximal and dont know any differant and bum some C-12 or Purple from someone, and didnt know to adjust for it... Your on your head.. If you can get Sunoco standard or C-12. I switched to C-12 this year and it jets the same as the sunoco.

My overall feel for the Yamaha and this is if you are trying to make it compeditive (on the box) is you have to run it lean to the point that you have a little detonation after the race. My new Honda seems to make good power alittle on the rich side but I havent gotten it on the MCE Dyno yet.

Sorry for the novel here everyone. Please feel free to E-mail me off list if you need any other information. While I don't have the bike anymore I have all the info. Note to self.... keep all notes when selling your bike to someone that is faster than you are...

Bill Cole