Posts
246
Joined
9/22/2017
Location
Summit Hill, PA
US
Edited Date/Time
1/26/2018 3:06pm
I’m looking for some thoughts and opinions on what is causing this? The piston has the same striations directly behind the fronts. It’s directly in the front and back. The back striations are right over the ring pin. There is 30 hours of trail riding on this piston and cylinder since being replaced and honed.
The piston that was removed from the bike was in it when the bike was purchased and was in extremely bad condition. It had the same problem but I assumed it was because of the piston condition.
The piston that was removed from the bike was in it when the bike was purchased and was in extremely bad condition. It had the same problem but I assumed it was because of the piston condition.
1. I don't see any cooling holes in the piston for the exhaust bridge and that is causing the bridge to swell and cause the marks on the piston in the photo.
2. I see a lot of wear on the piston skirt. Looks to be from cylinder ports sharp from wear.
3.I see a good bit of blow by from the rings leaking combustion gasses.
Things to do:
1. have cylinder checked for wear. Then replate as needed.
2. Don't run 30 hours on a single ring set up as that is too long and creates excess blow by at the rings and excess piston wear.
3. Drill needed cooling holes in the piston below the rings to match the exhaust port bridge.
Paw Paw
I had a 2004 CR before this 07 and used it for the same riding. I had it since new and would replace the piston about every 15-20 hours but they were always in great condition. I felt like I was throwing out good pistons. I
started to leave the piston in for the riding season (warm spring until colder temps only riding Sunday’s) and they would still look good. Going off the advice from fellow riders I never drilled the lubrication and never had an issue like this.
I’m going to take your advice on this one to see if I get better results. I’m also going to take my cylinder to a different shop.
Thanks
The Shop
This is why I don’t drill the holes because for every person that says to do it there is another saying no.
Vertex is the best piston.. give it a try. Together with one of those above 3 oils and mix it 40:1. Make sure ya have the right main jet coz with denicol ya can't see any colour on a sparkplug lol
If you’re saying a new cylinder is 310, where is that from?
Check this out. I use one https://www.ebay.com/itm/CR250-07-AIR-BOX-SEAL-KIT-2002-2007-CR250R-SEA…
Pit Row
So i don't think it takes a few months . Motorsports has it in stock. Partzilla he can ask thats the cheapest one.
Have to pay to much tax in Holland over a cylinder what i buy in the USA. So the Uk is my way to go. Every car or motorcylce part we must pay taxes if we get it from outside europe. That's around a 25 dollar on a 100 dollar. In the end a cylinder from the USA cost me around 60 euro more then a cylinder ordered in the UK. Shit taxes lol
Things to watch for:
If you're using the stock 07 airbox, there are plastic nubs which protrude into the filter mounting plate where the filter sits flat against the airbox. The nubs interfere with the filter mounting and can allow dirt to get past if the filter is not greased where it sits against the airbox. Try installing the empty filter frame (filter removed) onto the airbox and install the wing nut. Observe the perimeter of the filter frame and observe that the filter frame does not sit fully down flat onto the airbox mount even with the wing nut tightened. To fix this, you can purchase an aftermarket filter mounting plate, or use a 2001 and earlier stock CR250 metal mounting plate. You'll need to drill out the nubs, but the older CR250 plate bolts align perfectly with removed nubs. You'll also need a plastic 2001 and earlier filter frame if you go this route.
Also, there is a foam gasket between the airboot and the outside of the airbox where the airboot mounts on. The foam degrades over time then and allows dirt to get past. Replace when you are installing the new mounting plate.
Also, if you are using an air filter that has a rubber grommet underneath the wing nut, be careful not to over tighten the wing nut. This can cause the rubber seal to flex and allow dirt to get past between the grommet and the filter. To solve this, we use gasoline resistant Seal All to glue the foam to the rubber grommet. Start with a perfectly clean and dry air filter with no oil on it and allow the Seal All to dry overnight. Silicone will decompose in this environment, do not use silicone.
get some good oil for the mix and bring back the smile on the red.
Twin air power flow kit i have it on the cr85 not on the cr250.. take the airbox apart, clean it and put some fresh silicone sealant between it. Job done
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