2005 CR250 cylinder problems

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5/20/2021 12:32 PM

Hi guys!
Im new here, im from Finland and i need your help since im out of ideas..

So i have this ’05 CR 250, it got a lectron carb and a VHM cylinder head, the rest of the engine is in stock form. I bought it in april from sweden, the engine is fully rebuilt 10hrs ago. He put a freshly nikasil plated cylinder on and a new piston before he sold it. I rode 2 hrs and the piston and cylinder was badly scratched on the exhaust side, since i heard it’s a problem on these hondas i just tought it was a poorly made cylinder.

I got a new nikasilplated cylinder from blixtenracing in sweden, they are a very respected company specialized in cylinder plating and fixing them, never heard a bad review about them and their work.

So i got the new cylinder home on tuesday and put it all together, gave her 3 heat cycles on the stand and took the pipe of just to check everything looked okay, and it didnt.. the intake side of the cylinder i badly scratched already without even riding on or putting any load on the engine.

Anybody here who have any ideas or knowledge what the hell is causing this? As i waited for the new cylinder i put i new crankseals, had airboot, carb and intake of to make sure everything is clean. As i fired the bike up the first time i sprayed carb cleaner just to make sure it isnt taking air anywhere. Adjusted the carb and gave her more fuel also just to be on the safe side.

New cylinder after 3 heatcycles.
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5/20/2021 1:45 PM
Edited Date/Time: 5/20/2021 1:46 PM

Did you drill holes in the piston at the exhaust port bridge? If not, it will continue to do this. The holes allow cool fuel to lube this bridge and without it the bridge will get too hot and cause what you are seeing.
Also: What was the ring end gap?
What was the piston to cylinder clearance when you put it back together?
What fuel mix are you running? Is it fresh?
Did you check or set your squish?

Paw Paw

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5/20/2021 1:54 PM

Yes i drilled the holes in the piston, but in this case that dosent affect since it scratched on the intake side of the cylinder, i have to pull it up again to get a better look on the whole cylinder.

Gaps are within factory specs, gas is fresh and i run 3% oil in the gas.

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5/20/2021 5:09 PM

The photo posted is of the exhaust side.

Paw Paw

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5/20/2021 6:25 PM

Awesome looking bike. Shame about the problem. Pull the head and cylinder off and post some more pictures.

From that picture and you saying the intake side is marked up too, it sounds like the bore may just be too tight.

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5/20/2021 9:37 PM

Paw Paw 271 wrote:

The photo posted is of the exhaust side.

Paw Paw

The piston is down, it is the cylinder wall you are seeing on the photo.

Yeah i will have to take it apart again to get a better look at things!

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5/21/2021 5:43 AM

I'm like PawPaw, I thought we were looking at the piston at TDC. blush

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5/21/2021 6:46 AM

Paw Paw 271 wrote:

Did you drill holes in the piston at the exhaust port bridge? If not, it will continue to do this. The holes allow cool fuel ...more

Serious question here - If drilling 2 holes in the piston skirt, at the exhaust bridge location, is recommended on certain models, why the hell don't they come out of the box with the holes already there???

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5/21/2021 9:12 AM

Got the cylinder of, and the marks look exactly like the ring end gap is too tight, double checked it again and the end gap is 0,50mm and the service manual says 0.40-0.55mm so i cant think about anything than bad nikasil plating? I have to contact the company who did it.
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5/21/2021 10:05 AM

Did you degrease and wash the bore after you got it from the plater? I know it sounds trivial but I've seen the debris from sandblasting and prepping the cylinder prior to plating mimic a tight ring gap. Basically, the debris works its way out and ends up in the ring groove and binds the ring. If I look closely and the left rear transfer upper edge, there is a pretty good nick in the plating.

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5/21/2021 10:15 AM

Yep, degreased it, washed it and blew with compressor every waterchannel and everything carefully 3 times before installing it

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5/21/2021 11:24 AM

Paw Paw 271 wrote:

Did you drill holes in the piston at the exhaust port bridge? If not, it will continue to do this. The holes allow cool fuel ...more

mxracer666 wrote:

Serious question here - If drilling 2 holes in the piston skirt, at the exhaust bridge location, is recommended on certain ...more

These are hole that need to be custom placed for proper fit as that bridge is not in the same exact spot on all cylinders. The holes are needed.

Paw Paw

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5/21/2021 2:58 PM

The fact that the scuffing is full circumference and appears to go below the bottom ring line makes it look like the bore is too tight. I assume the piston is scuffed from top to bottom like the bore.

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5/21/2021 3:39 PM

Mr. Robinson wrote:

The fact that the scuffing is full circumference and appears to go below the bottom ring line makes it look like the bore is ...more

Nope, nothing on the piston.. a friend of mine was talking to someone on some two stroke forum and a guy there had a cylinder wirh the same scuffing. He said it happend to him several times too with replated cylinders and got scuffed like that after first start up and all the ring and piston gaps were okay. So i guess i just got unlucky and got a crappy done nikasiled cylinder..

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5/21/2021 5:36 PM

It must be. Looks about like raw aluminum.

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5/21/2021 6:56 PM

Can you feel any of the scratches with your finger nail?

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5/21/2021 6:56 PM

Search cylinder Streaking or stripes. My 88 RM 250 cylinder looked like this after 10hrs of use, was replated by Powersealusa. Everything thing was in spec, piston looked great, I pulled it apart as it is a single ring & I wanted to inspect my work. Sent photos to powerseal, they asked if I could feel scuffs in cylinder with my finger nail, I could not, they said it’s fine, offered to hone it but said it really was not nesseary. Have also read some builders believe it’s from to many heat cycles without a load on engine, and the rings are not seating properly. And finally was told to avoid synthetic pre mix until after break in....

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5/21/2021 11:28 PM

sandman768 wrote:

Search cylinder Streaking or stripes. My 88 RM 250 cylinder looked like this after 10hrs of use, was replated by Powersealusa. ...more

Alright! Have you had any problems riding the cylinder looking like that? Feels kinda scetchy too me and im afraid it’s gonna lock up right on the lip off a jump.

Can’t feel anything with my fingernails so should be fine to use in that matter.

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5/22/2021 4:08 AM

Sandvik74 wrote:

Alright! Have you had any problems riding the cylinder looking like that? Feels kinda scetchy too me and im afraid it’s gonna ...more

Since you have it apart, I would double check all your tolerance”s just to be safe. I would also contact company that did the replate & send them photos of cylinder for their input.

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5/22/2021 4:39 AM

sandman768 wrote:

Search cylinder Streaking or stripes. My 88 RM 250 cylinder looked like this after 10hrs of use, was replated by Powersealusa. ...more

Sandvik74 wrote:

Alright! Have you had any problems riding the cylinder looking like that? Feels kinda scetchy too me and im afraid it’s gonna ...more

sandman768 wrote:

Since you have it apart, I would double check all your tolerance”s just to be safe. I would also contact company that did the ...more

Yeah i have double checked all tolerance’s and they are all in spec. Tried contacting the company all day by phone and via email but no answer..

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5/22/2021 5:49 AM

Honestly I think it’s fine. It’s not uncommon to see streaking in a new two stroke bore and a lot of times the lighting and or camera flash makes things look worse in the photo then they are. If you can’t feel anything with your fingernail and can still make out some cross hatching in the streaks I would run it.

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5/22/2021 7:01 AM

soggy wrote:

Honestly I think it’s fine. It’s not uncommon to see streaking in a new two stroke bore and a lot of times the lighting and or ...more

Yeah, think i’ll put it all back together again and go ride it.

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5/22/2021 2:14 PM

Ktm calls it pearling, and it was present in the new 300s i did a top-ends in during the piston recall a few years ago.

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5/23/2021 7:17 AM

My new 2020 ktm 150sx looked like that too. I noticed it when I put the rk head on. It had .1 hrs (6 minutes). I was thinking the same thing. No problems.

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5/23/2021 10:18 PM

It’s not acceptable for me either a cylinder looking like that after a cuople of startups.. but don’t have much of a choice right now but to run it, the riding season here in Finland is so short and dont feel like waiting a couple of weeks again to get it replated and then it’s probably the same thing again..

Unfortunately there is no new oem cylinders available here before fall, they are all sold out.

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5/24/2021 12:23 AM
Edited Date/Time: 5/24/2021 2:09 PM

My suggestion:
Ride it so you can enjoy your season (you only get so many in a lifetime) and treat the whole situation as an experiment. Does it maintain good compression throughout the season? Is it worse when you tear it down at the end of the season and what does it look like then? Learn from it - so you know what that *apparent* condition does to performance. Maybe it is a non-issue afterall?

In spirit, I am with Mr. Robinson all the way! But I do look back on many missed riding opportunities due to stuff like this and kick myself. Live and learn.

Lastly, definitely document it so you can attempt to resolve the matter later with the shop, but don't throw away your season.

My 3 cents. Enjoy the ride!

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Contact me at: VitalMX123@outlook.com

5/24/2021 1:18 AM

Yeah that what i was thinking too, was riding about 1,5hrs yesterday and no problems so far, feels like i have nothing to loose here. If it breaks it breaks, at least i get too ride some instead of waiting for parts all summer and not riding at all. And like you said, you get knowlegde from it in the future too and get to pass it forward to other people.

It won’t probably last as long as a cylinder with no scuffing in it but if i get 20hrs from it it’s a win situation at this point.

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5/24/2021 4:40 AM

RGaede wrote:

Ktm calls it pearling, and it was present in the new 300s i did a top-ends in during the piston recall a few years ago.

What did KtM do with the cylinders?

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5/24/2021 6:28 AM

RGaede wrote:

Ktm calls it pearling, and it was present in the new 300s i did a top-ends in during the piston recall a few years ago.

sandman768 wrote:

What did KtM do with the cylinders?

They advised that it was normal and they wouldn't do anything about the cylinders. They just said to put the new pistons in. These bikes had 0.0 on the meter, only run time was from the dyno at the factory.

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5/24/2021 2:03 PM
Edited Date/Time: 5/24/2021 2:11 PM

RGaede wrote:

Ktm calls it pearling, and it was present in the new 300s i did a top-ends in during the piston recall a few years ago.

sandman768 wrote:

What did KtM do with the cylinders?

RGaede wrote:

They advised that it was normal and they wouldn't do anything about the cylinders. They just said to put the new pistons in. ...more

Super interesting, thanks for sharing that tidbit.

"The older I get, the more I realize how much my anal retentiveness has set me back." -Me, just now

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Contact me at: VitalMX123@outlook.com