KLX 250 ( 300 ) camshaft mod by Marcelino
#1081
04-15-2020, 01:41 PM
OK Back at it,after careful examination it appears that while the rivets in the acr are still tight the wear in the holes in the pendulums is such that there is too much lateral movement.I believe this allows the lever to contact the follower under certain conditions as it spins,as explained in the previous posts.In Oldboy's Damaged Valve Lifter post,klx678 commented that it might have something two do with the compression release,but other than that it's been quiet.While I realize conventional wisdom suggests spring removal is all that's needed when doing the MCM mod,I've been uncomfortable with doing this and after seeing this damage I'm kind of wary of the whole unit.Thousands of miles on my KLR yielded no problems at all with the acr but the revs were,at least in my case,substaionaly less.Quoting Klxster,"from those that can learn from"one data point"",one and a half if you include Oldboys issue,I'll be removing the acr(no big bore in my future,although some may consider all this a big "bore") and going from there.My suggestion is to keep an eye on this and hope that these are the only two that show up. And please,everybody stay safe and well!
#1083
04-16-2020, 01:05 AM
Ok, got it.. You don't trust the KACR mechanism so you are going to remove it completely..
Except for what you are showing us, I can't remember any reports of lifter damage from the KACR. But as you say, it only takes one solid case to show that it is possible..
Pulling the spring totally deactivates the KACR. The mechanism will go "inert" within the first revolution of the engine on a startup..
Except for what you are showing us, I can't remember any reports of lifter damage from the KACR. But as you say, it only takes one solid case to show that it is possible..
Pulling the spring totally deactivates the KACR. The mechanism will go "inert" within the first revolution of the engine on a startup..
#1084
04-16-2020, 02:02 AM
In an ideal world I'd love to reposition the acr as suggested in the otriginal MCM post and leave it at that,in fact that was my intent until I saw the damaged follower and that got me thinking,then I stumbled on Oldboy"s post and pic and that changed my plan.What worries me is not so much the lack of function (well documented as not necessary on a stock bore) as the now useless parts rotating at speed and "maybe" causing other problems such as what I found in my motor.Now to get on with putting it back together so I bake up recipe #1,can't wait. Thanks
#1085
04-28-2020, 09:00 PM
Righto, MCM done. I completed the mod without removing the cam cover. As the bike is still under warranty I wanted to touch as little as possible. I only had to move the fan for better access. Left petrol tank on as there was just enough room to remove the engine cover, and everything is from the side access, not above.
Sequence
Took me about 2 hours start to finish.
Took it for a run in the mountains and certainly feels different. Not arm stretching, but definitely an improvement, and needing less throttle for the same acceleration. Maybe faster reacting to throttle. The note is different as well. Seems to actually sound like a bigger motor. A bit easier to get the front wheel up, and has the low down torque, that on a steep climb that I normally took in 2nd, I took it in 3rd and it didn't even blink. Lots of potential to get me in more trouble with my right wrist having a higher expectation compared to my actual skill level... I don't think it is running lean, but may respond to some carby adjustments. On the ride home I tested pulling out the choke while cruising at 7000 rpm, and there was no change at all. No rev change and no speed change. Read that an indication of lean is if it picks up with applying choke. Does that sound about right for the mix? I don't know a lot about carby tuning and behavior.
Anyway, happy I got the mod done. Thanks all for your assistance. With all the mods, I think it is closer to a DRZ 400 in power than the original stock bike. I actually think I won't have a need for any more power.
Sequence
- Remove spring from KACR. Can easily access it.
- Remove cam chain tensioner adjustment bolt and spring.
- Add marks. I also marked the chain so that I was sure I only moved 2 teeth. The exhaust side shows this clearer.
- Set to TDC and remove bolts. One sprocket at a time. I couldn't clearly see the sideways T mark (as per the manual), but knew I had TDC as the IN and EX were right way up and the cams were pointing away from each other and up.
- Ease the sprocket off the cam with a screwdriver. The sprocket will drop a bit due to tension of the chain adjuster. I tried to keep the chain reasonably tight so that the chain didn't come off the bottom or off the cam chain guide. Don't know if it could do this, but wasn't taking any chances. I also didn't want the chain adjuster to have a chance of moving in another notch. In reflection I probably would have been better to remove the tensioner assembly completely, and add back in after the sprocket moves.
- Rotate the cam 2 teeth counterclockwise for inlet and put the sprocket back on the cam. This was pretty easy to get back on with a screwdriver as a lever between the sprocket and the cam. Conveniently there is a gap between the 2 parts to do your levering. repeat for ex but clockwise.
- Advance/retard the cams the half a tooth needed to line up the bolt holes.Add back in your bolts and tension up. Don't skip the fact that the bolts require non permanent locktite. I used 243 as it is better in the presence of oil.
- Re-assemble, manually turn over with sparkplug removed, Then turn over with key, Add spark plug and start. I gave it about 3 hours as 243 is about 60% strength after 3 hours, then went for a ride.
Took me about 2 hours start to finish.
Took it for a run in the mountains and certainly feels different. Not arm stretching, but definitely an improvement, and needing less throttle for the same acceleration. Maybe faster reacting to throttle. The note is different as well. Seems to actually sound like a bigger motor. A bit easier to get the front wheel up, and has the low down torque, that on a steep climb that I normally took in 2nd, I took it in 3rd and it didn't even blink. Lots of potential to get me in more trouble with my right wrist having a higher expectation compared to my actual skill level... I don't think it is running lean, but may respond to some carby adjustments. On the ride home I tested pulling out the choke while cruising at 7000 rpm, and there was no change at all. No rev change and no speed change. Read that an indication of lean is if it picks up with applying choke. Does that sound about right for the mix? I don't know a lot about carby tuning and behavior.
Anyway, happy I got the mod done. Thanks all for your assistance. With all the mods, I think it is closer to a DRZ 400 in power than the original stock bike. I actually think I won't have a need for any more power.
Toph
#1086
04-28-2020, 11:24 PM
Do you mean the cam chain tensioner? If yes, I took the spring out first, but can be done any time prior to moving the cam sprocket. Or when you say remove the accessible bolt, are you talking about the access hole to see the T to know you are at TDC? I used a big washer and vice grips. Apart from that, after you take the cylinder head cover off, the only bolts you need to touch are the cam sprocket bolts.
#1087
04-29-2020, 12:56 AM
Do you mean the cam chain tensioner? If yes, I took the spring out first, but can be done any time prior to moving the cam sprocket. Or when you say remove the accessible bolt, are you talking about the access hole to see the T to know you are at TDC? I used a big washer and vice grips. Apart from that, after you take the cylinder head cover off, the only bolts you need to touch are the cam sprocket bolts.
Sorry for not being clear. I mean the bolts holding the sprocket to the cam. If you put the engine at TDC then you can’t access the lower bolt. I’m assuming you remove the lower bolt, put the engine at TDC then remove the top sprocket bolt then slide the sprocket off the cam? Like you I want to avoid removing the cam completely.
Toph
#1088
04-29-2020, 01:54 AM
Yes that's it. I found tdc first, then rotated enough to remove the bottom bolt, rotated back to tdc and loosened the top bolt, checked that I was still at tdc and the lines were still as per the 'before' pictures, removed the top bolt. I found that marking the chain helped to know I moved 2 links, as it is a bit fiddly getting all the teeth out of the chain to do the rotation.
From what I can tell, I may have been the first to do it this way, so please add a post when you finish to record how it worked for you.
From what I can tell, I may have been the first to do it this way, so please add a post when you finish to record how it worked for you.
#1089
04-29-2020, 06:12 AM
Also, when I did mine I made sure I maintained a bit of tension on the chain, so was pretty confident that the cam chain adjuster could not have moved in (even though it shouldn't with the spring removed). But if there is any doubt then just take off the adjuster assembly and reinstall it after the mod. The spring will click it back to where it is currently set after re-installation.
Cheech
Cheech
#1090
04-29-2020, 01:33 PM
Thanks for the confirmation and the tips. I removed the tensioner completely but will defiantly keep tension on the chain. Ran out of time yesterday so hopefully I can get to it later today schedule permitting. I'll report my thoughts when done.
Toph
Toph