The valve timing has nothing to do with the size of the bore. I still kind of think jhoffy bit off more than he could chew. One side of the cam mod done incorrectly and wham-o.

 

Hey TNC,

Some of the silence may simply be "posting fatigue" from the sudden flurry of activity on this great modification. Marcelino's hands must be tired from all the typing he's done. You've got to admit it landed like a bombshell on everyone. This time last week I was ordering a 43T rear sprocket for a quiet compromise on power delivery for off-idle over vs the stock gearing and then all of a sudden Marcelino's post hit us all like a hurricane.

To answer your question, mine is a 250 with all the mods in my signature line. There's probably a BB 351 winter mod in my future but right now I'm squeezing my 250 for what she's worth.

I like Marcelino's mod. I think it works very well, so far.

Hope this is useful...

 

the sound your hearing is people counting their change to buy the web cam. Those pictures were traumatising. $350 for the cams sounds cheap compared to the replacement parts list of that grenaded top end!

 

Yeah, I gotta say the catastrophic failure has dampenned my enthusiasm somewhat

I need to think very carefully about this mod. I would love the extra (and shift of) power, but the bike is my daily commuter. I have a car as a backup if the worst happens though. I think I would rather do this mod than slap a 351 kit on to get extra power.

I think I would like to do the mod without changing the ACR first just to see how I go and whether I like the power shift. If I do, then I know I need to get the ACR sorted out which will mean taking the bike off the road for a week or so. I am thinking over the Christmas period might be a good time to do that. What I like about this mod is that it can be tested first for free (if you DIY) and reversed back to stock without any worries really.

Until I do it though, I will be reading up on other peoples experiences to see how they get on with it!

 

I'm still very interested in this mod. I just work slow since I'm learning as I go.
I do wish a few folks could give the clearance specs for before and after.
I have a mechanic friend with one of those color bore scopes. It has a right angle attachment. I'm wondering if it will fit inside the plug hole so I could take a look. I sure wouldn't want to loose it inside there. Anyone have one of these they could try and take a look?

 

kansas, you're probably right on the posting fatigue. However, I too am intrigued by this mod and wonder if jhoff's experience threw a wet blanket on the issue. I was really more curious if someone on the forum was preparing to do a 351 where such a measurement could be undertaken while the bike is being reassembled anyway. If someone could supply a used, intact base gasket and used head gasket, the absolute closest piston/valve clearance could be checked on this new build without sacrificing a gasket set.

RaceGass, yes, I think a lot of light was shed on the Wed Cam issue, and that is always an option.

I'm still somewhat amazed that this mod would yield a 25% or so horsepower benefit...about 5hp, correct? Yes, I get the concept of moving the powerband down the range for more generally useful rpms. That's what I did with my stroked Chevy engine. I'm obviously no authority on this issue, but that's a lot of power for a relatively simple mod. Pretty impressive if everything shakes out correctly.

 

Hey Arctra,

I was looking at your signature line. You're running jets of such size with a 250? What do you folks down under get from Kawi that we don't have in the U.S.?

I have a feeling that my riding style is a bit, shall we say, milder than yours?

If I was running those jets there would be raw fuel squirting out my exhaust!

BTW, if you experiment with the camshaft mod without the ACR repositioning, the bike will ride fine but be impossible to start while hot. That's how I first tried it and I can testify to it first hand.

Good riding.

 

He has an FCR carb, doesn't he?

 

Still, with a 250?

Be advised that although I have more than a few years of maintenance/inspection experience, my KLX250 is my first bike so there may be some nuance that I'm missing...

 

I don't think anyone paying attention to posts from the past few days would let jhoffs actions stop them from trying this mod. Well, maybe the 351 crowd and if they installed that 351 by themselves I think they would have the ability to check clearances too. Lets face it, jhoff was wound up like a kid on crack. I don't think this mod done properly could've caused his problem. Perhaps he didn't skip the teeth on the exhaust sprocket?
I think most folks, that want to try this mod, are probably waiting till they have time and it's too cold to ride.
I think KAW probably timed the cams like they did to make the bike "cleaner". Marcelino just found a way to reverse it for FREE.
You know that drag racing show on Speed channel where three guys try to geuss the times of the cars? I think it's funny when a guy with an old Pinto or something proudly tells how he's spent thousands on a big engine build with nitrous, etc. makes a run and then a guy pulls up in a stock CTS, Porche, Nissan, etc. and he runs a faster time then turns around and drives his car home. That's just some perspective to keep in mind when moding our bikes.
Anybody have a bore scope?