Can someone tell me if the Marcelino camshaft mod works with the big bore 351? I thought I read in the 85 pages somewhere that it's not worth doing. If not, how does the power compare to the 250 with the Marcelino mod and the big bore 351 kit installed.

 

That depends on what you add to the engine on top of the 351 kit. According to Bill Blues' dyno charts, and mine, a stock bike with only the 351 kit vs a 250+MCM+exhaust slipon+lidless+proper CVK setup, shows the same HP with the 351 +2.5 lb ft of TRQ.

While the above is true. it is also true that adding a slipon, good CVK setup ect ect to the 351 will ramp HP and TRQ well above a "fully performance enhanced" 250..
If I remember correctly, add a slipon and a good CVK setup, and you can expect 26hp, a TM36-68 gets you to 28hp, add webcams for 30hp.. To any config, add a full exhaust system and count on +2 hp..

My issue with the 30-32 hp KLX351 is the huge cost to get there - I seem to remember something close to $2000... ( Barnet heavy Clutch springs are going to be needed, sooner or later, as well - assuming your clutch is in "tip top" shape. Otherwise, add in plates and friction plates - $160.00 http://www.barnettclutches.com/502/k...i-klx250s.html)

 

Superior cam timing works for any displacement. As long as there is not an issue with valve to piston clearance with the 351 piston, the results should be incredible..

I just re-read the first 15 pages - it does work on the 351..

 

My current set up is the MC mod, 300 exhaust (tip removed) with head pipe, stock CVK with dyna jetting, performance air filter, backfire screen removed and 200 snorkel. The bike runs very strong and its a huge improvement over stock. I have know idea on HP. I figured the next step would be the 351. I dont want to spend $2000 but could see $1,000. Looking for the best results for that kind of cash.

 

Your set for adding just the 351 kit and a rejet.. No one has a "AFR chart verified" CVK setup for the 351 but good running 250 setups seem to work ok..

 

Thanks for the info. I'll start with the 351 first the probably look for the TM36-68 next. I just have to find a reasonably priced one. A quick search shows around $350 which is a little pricey for 2 HP. Did they use the carb in another application that could be swapped into the KLX?

 

If this were really superior valve timing... which it's not. It's an attempt by somebody who truly does not understand valve timing to duplicate something, based on some fallacies. The justifications used by Marcelino to come up with these numbers are absolutely ludicrous.

 

Funny part is I saw pretty much the same "ludicrous" method used by Joe Minton, pulling the Honda CB700SC cam timing from 133° down to around 110°, similar technique and similar reasoning was given in the article. Joe Minton was a pretty well respected motojournalist and mechanic having done numerous articles back when magazines actually did "how-to" articles.

That was the main reason I did the modification, I had no idea who Marcelino was, but I knew darn well who Minton was and that the two had pretty much the same reasoning.

Art Friedman, former editor of Motorcyclist had this to say about Minton, "Joe Minton was unmatched in his knowledge of how to make a motorcycle work better. " - Art Friedman, A Fun Ride. Probably near on par with the late great Gordon Jennings.

The Nighthawk S actually lost a minor bit on the peak HP, but had gains at virtually all rpm from that point down - power gain where it mattered, not just the peak number. Marcelino did actual dyno testing too, so it's hard to argue with hard numbers.

Now if you can give similar justification why it is an incorrect move to work the cam timing around where they did I'd be glad to read it. Especially if dyno numbers could be produced to show the opposite of what was given in the first few posts of this thread.

 

I can never understand statements that dismiss something with no explanation. You need to explain your point and the words "fallacies" and "ludicrous" don't suffice.

 

I have in the past, but will address them once more, and in better detail now, as I have time.

Absolutely not true. It makes no more or less noise from either end than what should be expected of a 250 2 stroke. Note all the threads where people with an aftermarket exhaust complain about how it's too loud.

Somewhat contradictory, it does or it doesn't? It responds exactly the way one would expect a 250, 4 stroke dual sport motor to respond to such mods. There are no surprises here.

None of those things are indicative of intake or exhaust lobe centerline. If you dispute that, please feel free to back it up with facts.

These numbers are typical for just about every 4 stroke engine in existence. Lobe centerline does not determine the RPM range. That is accomplished by duration. It can be tweaked - to a small degree - by altering centerline, but is, and should only be used as fine tuning, and not a corrective measure. While it is common to fine tune when too much duration is present (you can add duration, then shorten up BOTH centerlines to help broaden the RPM range), it's not when the duration is too little, which is the case here.

Desmodronic distribution? Such a thing does not exist. Desmodronic is a term used bu Ducati and Mercedes to describe the way a valve is actuated, and has no determination on power band, or power. The KLX has ignition advance.


Well, you did it for the wrong reasons then. What was done in that application was precisely what I described as fine tuning by shortening up both centerlines when too much duration is present. In that case, both numbers are in the extreme, and both centerlines were advanced roughly the same amount to achieve that goal.

As far as his dyno numbers are concerned, I believe he provided only a single post modification dyno chart?

Personally, and I admit I haven't read every single post in this thread, has anybody actually degreed the cams, or only relied on his estimations of what the actual timing might be? With a mod like this, it's unheard of to move the cams, and not degree them with the proper equipment.

And for the newbies that don't know, I am in the camshaft business. I am a custom cam grinder, and put my own profiles together for many applications. I have been building race engines for exactly 40 years this year, and there is nothing more in this for me than educating the people who choose to ride, mod and enjoy the bike I enjoy so much. I have nothing for sale.