KDX220 update + question

[JZ05220r]

Some of you might remember all the trial and error I went through trying to get my 220 running how I wanted. I ended up redoing the top end again, and it’s back to a full 220 setup: stock internals, carbon reeds, and an FMF desert pipe. Since spring, I’ve actually been able to enjoy the bike, and it’s been running great with just some minor tweaks here and there.

One recent change was dropping the pilot jet from a 42 to a 40. That seemed to clean up the low-end throttle response I used to get these little hiccups during part-throttle acceleration that felt like it was running a bit rich. The 42 also tended to load up more at idle and would dip faster if I let it sit too long. The 40 definitely seemed to have helped (not completely) in both areas to the point where I am fully satisfied.

With the airbox snorkel removed and still using the stock 33mm carb, does this jetting still sound like I’m in a safe range? Thanks

[SS109]

I would say you're good. What truly matters is how it runs. Also, if your air screw is between 1 and 2 full turns out then you're spot on.

For comparison, I run a 38pj and my lowest altitude is 1600ft asl up to about 2500ft.

[JZ05220r]

I would say you're good. What truly matters is how it runs. Also, if your air screw is between 1 and 2 full turns out then you're spot on.

For comparison, I run a 38pj and my lowest altitude is 1600ft asl up to about 2500ft.

Thanks, just needed some reassurance

[Chuck78]

Hey James! I recall all the difficulties you had with what appeared to be the cooling system becoming pressurized, presumably from a compromised head gasket seal.
Lately, I'd noticed a bit of the same with my bike. I have a 1.8 bar radiator cap with thermometer gauge, higher rating than stock, but the bleed port plug's o-ring on top of my left radiator seems to allow a few drips of coolant past it on technical challenging slow hot rides, I've noticed this year. Last year, I had similar but from the coolant flange gasket on the cylinder head. I'd found that gasket surface less than perfect and a bit corroded, so I thought that was the issue. The newer issue brings to light similar as to what you'd found.

What I'm more recently found was that our fellow member here, Darryl aka kdxdazz, had posted a video a while back that had gone unnoticed by most of us. With his RB modified head, keep in mind his was a 220 Sr head that required a different approach to get the same chamber result, he had found that he was basically running out of compression height for the head gasket due to the dowel pin bottoming out in its registers in the cylinder and cylinder head, therefore not allowing full torque on the head gasket around the dowels. He had stated he was going to grind a little off of the ends of the dowel pins and reinstall after checking everything else out. I'm not sure what the outcome was, but this sounded very highly likely to be perhaps the cause of both of our issues of a less than perfect sealing head gasket.
I know you had checked and resurfaced the head gasket surface on that RB head that you sold me a couple times. I also have an RB head on my bike I believe, it definitely looked like it had some work done to it when looking at it with a borescope, it could be a Fredette head however, as the previous owner was from illinois but the Jeff Fredette modified heads I have seen, are really just shaved with the chamber not touched, this one definitely looked to have the chamber modified.

I plan to do a top end tear down at some point to clean the KIPS, measure the piston ring end gap and cylinder bore diameters, inspect the Wiseco piston the previous owner installed, replace the KIPS packing seal, and also now check this dowel pin depth versus it's bore registers

[JZ05220r]

Hey James! I recall all the difficulties you had with what appeared to be the cooling system becoming pressurized, presumably from a compromised head gasket seal.
Lately, I'd noticed a bit of the same with my bike. I have a 1.8 bar radiator cap with thermometer gauge, higher rating than stock, but the bleed port plug's o-ring on top of my left radiator seems to allow a few drips of coolant past it on technical challenging slow hot rides, I've noticed this year. Last year, I had similar but from the coolant flange gasket on the cylinder head. I'd found that gasket surface less than perfect and a bit corroded, so I thought that was the issue. The newer issue brings to light similar as to what you'd found.

What I'm more recently found was that our fellow member here, Darryl aka kdxdazz, had posted a video a while back that had gone unnoticed by most of us. With his RB modified head, keep in mind his was a 220 Sr head that required a different approach to get the same chamber result, he had found that he was basically running out of compression height for the head gasket due to the dowel pin bottoming out in its registers in the cylinder and cylinder head, therefore not allowing full torque on the head gasket around the dowels. He had stated he was going to grind a little off of the ends of the dowel pins and reinstall after checking everything else out. I'm not sure what the outcome was, but this sounded very highly likely to be perhaps the cause of both of our issues of a less than perfect sealing head gasket.
I know you had checked and resurfaced the head gasket surface on that RB head that you sold me a couple times. I also have an RB head on my bike I believe, it definitely looked like it had some work done to it when looking at it with a borescope, it could be a Fredette head however, as the previous owner was from illinois but the Jeff Fredette modified heads I have seen, are really just shaved with the chamber not touched, this one definitely looked to have the chamber modified.

I plan to do a top end tear down at some point to clean the KIPS, measure the piston ring end gap and cylinder bore diameters, inspect the Wiseco piston the previous owner installed, replace the KIPS packing seal, and also now check this dowel pin depth versus it's bore registers

Yes, with the head gasket situation that’s kind of a thing of the past. I haven’t even bothered checking as my coolant level in the overflow has remained the same with bike; Fully warmed up and cold. The engine doesn’t seem to be overheating.

I think honing in/hyper focusing too much on the coolant level with the cap removed and engine running could very well be the problem there. I think a lot, if not all of the bubbles were normal. I mean I’ve got a lot of hours on it currently and like I said, the level has not changed.

Yes I have heard about grinding the locating pins down. That’s actually one thing that Ron himself suggested to me a few years ago when I was first having the issue.

To sum it up I think my biggest weakness in the past is having an overly perfectionistic attitude. And I almost feel like I create some problems more than I actually fix them with that attitude. Good luck with the rebuild! I know you’ll be very meticulous and do a great job with it.