Top End Cylinder and Piston Pics

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#1
Last night I got my bike ready to take the top end apart. This morning before work I went out and dissasembled it. I have two pictures of the Jug. It appears to be fine but there was one area I wanted to see what yas thought. I plan on selling this bike very shortly. Im also going to take some pictures of the piston when I go back out. I plan on just putting a new ring on it. Ill see what you guys think after I get those pics up. It had a lot of carbon build up on the top of it and some brown areas on the sides. I guess they are burn spots? Also Eric or Rich if you can tell if porting has been done to this cylinder, let me know. It has a gator carved in the side of it and I have been wondering what its for and thought maybe it was the porters signature or something.

Couldn't get pictures to show here so you will have to view them at Yahoo. Here's the link... http://y42.photos.yahoo.com/bc/rm25...ida/lst?&.dir=/Top+End+Aug.+9&.src=ph&.view=t

You can see the burn marks in the first picture and a very small line just a little over an inch long that appears to be a slight scratch. The picture is showing the front of the cylinder just above the exhaust ports.
 

RM_guy

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#2
Your picture link brings me to a restricted area in Yahoo
 

MikeT

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#3
It doesn't look like it's been ported from the view I saw. If the bore diameter is within spec, I'd just hone it and put in a new ring as long as the piston doesn't have too many hours on it.
 
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#4
RM_guy: You have to have a registration with Yahoo. Then type in your username and password to view them. I've tried to make it so you don;t have to do that but I don't think it's possible.

MikeT: The piston has about a year on it but was never rode hard. The local Suzuki shop said racing the rings should be replaced every 3 races but rec. riding once a year. Then I went on to tell them it was a Pro X single rign design piston and they looked ta me like Pro X? And asked "Is it Wiseco Pro-X? And I said no it's NIKs Pro X and I think its made by LA Sleeve and they said they never heard of it. The I said if I do put a new ring on it will it need to be cross hatched again and they said no.

I got the pics of the Piston but I left it in the shop. The piston had a LOT of carbon on it. The top had about 2 finger nails on top of each other of carbon. The sides also had a alot of carbon. I put a little Dexron III on it and let it sit for a while and then took a tooth brush and scrubbed it off the sides and steel wool to get it off the top. How can I clean the carbon out of the ring groove? How do I cross hatch it myself? When you look at the cylinder in light you can see cross hatches in it. I started to take alittle carbon off then I decided to take the pics first to show you so you'll see how much was on it. I think the spark plug was probablly pretty old and not firing strong enough. Could this be the problem or could it be something else?
 
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#5
Everything I see in the pics looks fine. The brown marks are from blow-by due to worn rings. The carbon buildup is a little excessive from your description, but can be greatly reduced with careful jetting. If it were me, and my top-end was torn apart for rings, with a year of service on it, I would spend the few dollars for a piston. A complete top-end kit is only around $100, plus a gasket kit. For the cylinder, go over it lightly with a ball hone or a scotch-brite pad to clean it up and de-glaze it, and you should be fine.
 
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#6
Is a scoth brite the same thing as like a Brillo or SOS pad? I got a box full of them that I use for cleaning the plastic and oil on the swing arm when it flys off the chain. I cleaned all the carbon of the piston with Dexron III and Brillo pad. It looks pretty good. Don't see any MAJOR scratches at all and there's no scuff marks. There is a few tiny scratches here and there. I was hoping to clean the carbon off and find the piston numbers so I could order the ring but didn't see any writing at all. I know Pro X makes fractional increases for the NiKaSil and I don;t know which one to get. Im sure the previous owenr will probablly know if I call him but hes out of town. Only thing I saw was an R on the ring and it was face up.

Would the carbon build up be due to too rich of a jetting? I mix at about 40:1 (12oz. to 5 gallons gas).Im pretty sure the spark plugs probablly a part of the problem. I think thats why I was hearing knocks because it wasn't firing every now and then. It is pretty dirty looking so Ill try a new one then do plug chops until I get coffee brown on all three jets.
 
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#7
A scotchbrite pad is not the same thing as steel wool. Don't use steel wool on your cylinder plating, you run a good risk of damaging it. I use a wire brush to get the carbon off the top of the piston to read the numbers.

Yes, the excess carbon is probably from a combination of rich jetting and not running the engine hard enough to burn it off. Taking a plug reading is only useful for getting the main jet correct, it won't help you with the other jets. You jet the needle and pilot circuits by feel and response.

The "knocks" you say you heard are probably pre-ignition, caused by hot spots in the carbon build-up. Once you have a fresh top-end ( I still say you should change the piston, but that is just my opinion), switch to 32:1 (26:1 if you like to rev the snot out of your engine all the time) and start jetting the pilot first, then the needle, then the main.Plug color is not a good tool for jetting, other than a WFO reading for the main. It is more useful for telling you if the plug heat range is correct for your riding conditions.
 
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#8
I heard that if you put the bike up on a stand so the back tires off the ground and spinning freely you can start it and put it in 2nd gear and let the idle speed turn the back tire. You let it idle itself around for about 10 secs then push the kill button. Take out the plug and check the color. I also heard to find a pretty nice size hill and go up it at half throttle and try not to give it anymore or let off. If it pops or pings is lean if it blurbers like a 4 stroke its rich.

I have all the carbon off the piston and there just isnt anything there. Im going to try to contact Pro X in a little while and see if there's suppose to be a marking someplace.

Is a scrotch brite like one of those green pads?

I dont see how the piston can be affected. The only part touching the cylinder is the rings, right?
 
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#9
Originally posted by RM250Rida
I dont see how the piston can be affected. The only part touching the cylinder is the rings, right?
The piston wears as well as the rings. Once the piston starts to get loose, it starts to slap back and forth in the cylinder, rapidly wearing the cylinder plating. Before you decide that you don't need a piston, slide it into the bore and measure the clearances at the skirt with a feeler guage. There should be no more than 002"-.004" clearance. If the clearances are greater than this, it is time for a piston.
 

MikeT

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#10
Originally posted by RM250Rida



Is a scrotch brite like one of those green pads?

I dont see how the piston can be affected. The only part touching the cylinder is the rings, right?
Yes one of those green pads is a scotch brite pad. You just don't want any type of metal pad like brillo.

The ring is in primary contact with the cylinder wall but the piston also makes contact. Spanky is correct and the piston will begin to slap around in the cylinder.

I know the extra bucks for the piston is something you'd rather not spend but since you have already done all the work, and your bike has a lot of hours on it, I'd get the new piston.
 
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#11
Alright Ill probablly go with a Wiseco unless you guys recomend something else. It dont bother me that i have done all the work. I enjoy doing it thus I got up early before work and went out to work on it. I'd like to persue it as a profesion someday. Anyways will it need a fresh hone and/or cross hatch? When i use to take other cylinders up for a bore job or something they always said they needed the piston to mic or myke it. Will they need it if I have the local shop hone it out? Can I just cross hatch it with scroth brite and put it together? I was also planning on going with Moose's high compression gasket kit. Should I got with Cometic or is Moose good quality also?
 
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#12
Just remove the glaze from the cylinder with a scotchbrite pad or a ball hone, and reassemble. The cylinder does not need to be honed in the traditional sense, just deglazed. A Wiseco piston is an excellent product, but be very careful. The Wiseco piston is forged, not cast like the stock piston, so it is critical that you break the new piston in carefully and properly, or you run a very good risk of seizing your new top-end. Do a search on this site about break-in procedures, you will get plenty of info. I use Wiseco pistons exclusively, and have always been satisfied with thier product, but you have to break it in right.

The Wiseco piston kit will come with most of the parts you need for a rebuild. You will also need to purchase a wrist-pin bearing, a gasket kit, and a pipe gasket. The pipe o-rings will come with the gasket kit.
 
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#14
I got some new pictures of what part Im at now and some of the piston after I cleaned it most of the way off...
http://photos.yahoo.com/bc/rm250rid...ast=1&.err=Piston.jpg&.last=1&.err=Piston.jpg

Gonna go order the piston, rings, wrist pin, circlips, bearing, and gaskets now. Found out Pro X puts their numbers inside the skirt and its just a part number, not a size. Gonna go with Cometic because thats all Chaparral sells. When my friend rebuilt this bike back when he owned it thats what he bought and he said the o rings for the head to cylinder didn't fit so he had to go to the suzuki dealer and buy some factory ones. I hope this isn't the case again.
 
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#15
Just got the parts today and got it rebuilt tonight. I ran the cylinder and head up to the local suzuki shop. They ran a ball hown through it cross hatch it and deglaze it and also lapped the head for me, for free. I also got a new spark plug there and they told me I should get a BR8ES instead of a B8ES because the R (resistor) ones are harder to foul. Is this true? Well I got it warmed up and played witht he throttle for 5 mins then turned it off and changed the idle screw and the pilot air mixture. Put on some of Factory Effex's super pro 8" numbers and waited about another 2 mins and it was fully cooled. I started it up and warmed it up again then waited another 5 mins then shut it off. I then let it fully cool then started it up and ran it at 1/4 throttle. then let it cool, started it back up to operating temp and ran it at half. I pulled it back in the shop and am letting it sit until tomorrow. Tomorrow I'll probablly warm it up and run it at half throttle for about 20 mins then let it cool completely. After that it should be ready to rip. Hurt my foot pretty bad kicking it over. :p

My friend wants to race me tomorrow against his 98 CR250. It's completely stock, even the piston. I have fresh wiseco, cometic high comp. gaskets, pro circuit pipe and silencer, Boyesen rad valve, and twin air air filter. I also have a one tooth smaller front sprocket so Im goign to lose some top speed. He's also a better rider. Ill let you all know who wins. By the was my bikes a 92 RM250. Think I can take him? It'll probablly be just a darg race up a paved road by his house. Then we'll go down and hit the gravel banks. Cant wait, my bikes ready to go.