Or anyone that can help with this. Ok the problem is that when I get my 250 really good and hot it drops a lot of power.I feel because of lack of ring seal. (among other things I know) but my biggest problem seems to be ring seal when hot. So do you think gas porting the piston could help with this? For those who may not know gas porting is a process of drilling many small holes around the top of the piston these holes go down to just behind the top ring to allow combustion pressure to force the ring into the cyl wall. (tis is what normally seals the ring anyway. ring tension mearly holds the ring out so this can take place.)by gas porting the combustion pressure has a direct path to do it's job rather than having to go around the sides of the ring.
So I am looking for info on doing this to a 2 stroke has it been done does it help? I'm thinking that the cyl of any air cooled motor must get fairly distorted when hot on one side and cooler on the other and full of uneven temp spots. So it only stands to reason that more pressure on the ring would help to force it to seal to a not so round bore Right?

Jeff

 

Tes jeff that does work but the biggest problem with the 250's is it is a piston port motor. That means it uses the piston to block off the intake port insted of reeds. So when your piston get worn it does not do as good as job sealing off the intake port that is why you are loosing power when it gets hot. Just sounds like it is time for a top end. If you want tomake a 250 piston last longer take your cylinder and have it bored and get a new piston. Then put the piston on the rod and just set your cylinder on the bottom end. Rotate the piston to bottom dead center, and take a marker and go into the intake port and draw a line al the way around the port on the piston. So now you pull the cylinder back off. Now you have the out line of your intake port on your piston. Now take a 1/8 drill bit and dimple the piston 1/4 inch from outside of your line every 1/4 inch. This will use the oil to better seal off the intake port. That = better and longer performance. I do this on all the 250's that don't get a reed mod. And any of the 250's that are ported it is a must because you take away surface that the piston seals off the intake port.
I hope this helps.
AZ BAD BOYZ

 

Bodda Boom........ Bodda Bing....... Good info Dennis. Gas porting has always worked well for keeping power, but ring life as you know will suffer. Cant remember off top of my head, but I know someone makes a total seal style top ring.

 

Thanks alot guys for the help I did not know if gas porting worked well on 2 strokes. I may just do the dimple thing for now thats a good idea never thought of the oil helping to seal. the piston slap is getting a little louder than stock. So bubba do you know how much the ring life will be affected if I gas port? this quad is 7 months old has five months worth of hard riding every weekend on it does this seem like it's wearing out to fast? it still runs great but I can tell it's lost some power. when I rebuild is there a better type of rings avil? like moly or tool steel what works best in a 2stroke? sorry for all the questions but I like to work on my quad and want to get the most out of it when it goes back together. And I'm learning some cool new stuff here!
Thanks

Jeff

 

Jeff, gas porting was done a lot in the 60's in cars, specifically the pro-stock ranks in order to help power. There are differences in that concept and a wheeler by far. The major ones I can say would be: They were more than likely using cast iron rings at that time, and those would wear quickly and also cause top end wear on the cylinder. They were turning the small motors about 9500rpms, also increasing wear dramatically. If I'm not mistaken, isn't the wiseco rings a moly type ring? I never really addressed that issue, but figured that they were. There is no difference between the top and second ring, therefore I would see no harm in gas porting. The pressure on the ring while open in the exhaust port would be nothing, and it would start increasing as the ring was almost completey covered up. Maybe someone would chime in here that has either done it or had it done, but I like the idea. That's what keeps things going.

 

Thanks for all the info I'm gonna do it to the old loose stock piston thats in there now thats all im going to do. no new rings or anything this will be a test. To see if there is a noticeable improvement. I will let you know how it works out. I don't feel the need to test the dimples around the intake thats a no brainer in my opinion it has to help. But i'm not going to do it yet so I can see the results of just gas porting.
Thanks again.

Jeff

 

UPDATE!

The gas porting has been done 8 holes 3/32" dia. have been drilled into the top of the piston. I set them in from the outter edge of the piston far enough that only half of the hole breaks through to the ring land. The depth of the holes is almost to the bottom of the ring land. The measureing and drilling took longer than everything else.
It made quite the noticeable differance I mean you can really feel it ripping up and down the street before and after what a differance. The biggest differance is the responsiveness when you back off the throttle and get back on it WOW zero lag it's on the pipe and gone. overall power improved it still has the slight bog you get off the line with the 250's but I did not expect that to change. At any rpm where the pipe is working there is a noticeable power increase! I did not think I would get this much of a seat of the pants power increase. I thought I would be lucky to even tell by ripping up and down the street. Well I was worng majore improvment.
Keep in mind this was done as a test so nothing else was done. same rings same piston no honeing just the gas porting. And it shows quite a bit of wear so the performance gains can only get better. The true test will be next weekend there is a hill that I can only climb if the quad is cool when it's good and hot it won't make it to the top so i'm gonna try it good and hot if I make it this will really show the benifits of gas porting. I have not yet dimpled the piston around the intake and know this may be part of the hot power loss so if I make it up this hill hot just with the gas porting then once I do dimple the piston look out there will be no stoping me LOL.
I will let you know how the hillclimb goes.
With the improvement I have already seen you guys may want to consider offering this service with some of your mods. It will be coming back apart after some hard riding for the dimpleing and a inspection of wear too see if it wears noticeably faster with the extra ring pressure.
Thanks alot for you help Dailyrider and Bubba. Keep in mind I'm not asking for your trade secrets when I ask these questions I just like doing it myself and trying stuff that may not be the norm.

Jeff

 

You knowwwww..... I only ported it to the top ring thats how it's done in automotive 4 strokes. But what would happen if i drilled on through to the second ring???
Any input... is this a bad idea? Why only the top ring in cars? Hummmmmmmm what do you think bubba


Jeff

 

For mild applications that might not be a bad idea. I think I would run it for a while like that first and see what happens. Be careful if you have it ported and make sure the exhaust is well radiused to avoid any problems. Keep up the good work!

 

UPDATE!

The gas porting was a success went riding this weekend and it climbed the hill much better. I still can't get over how much quicker it respondes to throttle changes. It made so much of a differance that on the hills we climb if I stoped on any of them before I could not get moving agin it would just bog and move very slowly and not get into the power and it's clutched for a higher stall than the pipe should need. It's just so steep it takes a ton of power just to move if you get off the quad it's hard to even stand up without holding onto something thats the best I can desribe it. So it sucks when you don't make it and can't get going agin. Well I don't have that problem anymore now it's just not flipping over backwards I have to watch out for.
So now I will just ride it hard and often for a while and see how the wear on rings and cyl go.

Jeff