BB 351 or BB331?
Thread Starter
|
Senior Member
Joined: May 2015
Posts: 329
From: Kenora, NWO, Canada
1st Gear Member
I just emailed Bill and asked him if the 351 changes the stock valve timing and his opinion on the MCM mod. I'll let you know his response. Also someone here asked if there was an oversized piston when rebuilding time comes up. He responded with a yes and an oversize of .010. Also JE builds his pistons.
Senior Member
Joined: Aug 2009
Posts: 4,650
From: Delaware, Ohio
1st Gear Member
Not that they don't work together, but rather that it didn't do much, if anything, when going big bore. Not a negative, but not a positive, rather a wash.
Senior Member
Joined: Aug 2009
Posts: 4,650
From: Delaware, Ohio
1st Gear Member
MCM on the 351:
The 351 fellas did a lot of "screwing around" before they finished the mod fully/correctly. Also they were "jacking around" with jetting at the same time.. So it's kinda hard to follow to the point where they actually tested the mod "fully done".. I'll list some of the pertinent posts that I found -
Post #149, #161, #163, #196.. Take a look yourselves and make up your own minds..
Know this: Jhoffy put in a 351 kit, MCM, and some other stuff, all at once. He rode it a little over 100 miles and loved it, then the engine "blew up" for some unknown reason.. Most of those Jhoffy posts have been removed.
MCM must be done without error - you screw around with this mod, doing it without fully understanding what your doing, and you'll likely be looking for another engine - or at least another top end..
The 351 fellas did a lot of "screwing around" before they finished the mod fully/correctly. Also they were "jacking around" with jetting at the same time.. So it's kinda hard to follow to the point where they actually tested the mod "fully done".. I'll list some of the pertinent posts that I found -
Post #149, #161, #163, #196.. Take a look yourselves and make up your own minds..
Know this: Jhoffy put in a 351 kit, MCM, and some other stuff, all at once. He rode it a little over 100 miles and loved it, then the engine "blew up" for some unknown reason.. Most of those Jhoffy posts have been removed.
MCM must be done without error - you screw around with this mod, doing it without fully understanding what your doing, and you'll likely be looking for another engine - or at least another top end..
You are absolutely correct that the MCM needs to be done right, as does any messing with cam timing. Jetting can be screwed up and the bike only runs bad, cam timing is another story, as is doing a top end.
Senior Member
Joined: Aug 2009
Posts: 4,650
From: Delaware, Ohio
1st Gear Member
You ought to hear how the KLX650 starter labors starting that engine even with the compression release. I never looked, but they might even be the same starter, just different gear reduction or whatever.
Senior Member
Joined: Aug 2009
Posts: 4,650
From: Delaware, Ohio
1st Gear Member
I just emailed Bill and asked him if the 351 changes the stock valve timing and his opinion on the MCM mod. I'll let you know his response. Also someone here asked if there was an oversized piston when rebuilding time comes up. He responded with a yes and an oversize of .010. Also JE builds his pistons.
Member
1st Gear Member
Joined: Feb 2016
Posts: 43
From: Perth, Australia
1st Gear Member
This is just my opinion:
A good mod list would be - MCM, exhaust, jetted for lidless running. Do this all at once and the bike is a totally new animal with "biggy power".
Next add the TM36 for even more power everywhere, PLUS the added "new" performance that the accelerator pump gives you.
After enjoying all the above performance, if you want more, add the 351 kit and jump directly to 28+ HP and huge TRQ numbers ...
A good mod list would be - MCM, exhaust, jetted for lidless running. Do this all at once and the bike is a totally new animal with "biggy power".
Next add the TM36 for even more power everywhere, PLUS the added "new" performance that the accelerator pump gives you.
After enjoying all the above performance, if you want more, add the 351 kit and jump directly to 28+ HP and huge TRQ numbers ...
Thread Starter
|
Senior Member
Joined: May 2015
Posts: 329
From: Kenora, NWO, Canada
1st Gear Member
So it looks like the MCM mod is a no go for the 351. Here is the reply I got from Bill.
"All adjustments stay the same as stock.
If the timing mod is the one where the cam gear is re timed it will cause the valves to crash into the piston damaging the valves, piston & head.
Never had any one remove the acr with the 351 kit.
Thanks
Bill"
"All adjustments stay the same as stock.
If the timing mod is the one where the cam gear is re timed it will cause the valves to crash into the piston damaging the valves, piston & head.
Never had any one remove the acr with the 351 kit.
Thanks
Bill"
Senior Member
Joined: Jun 2013
Posts: 3,315
From: North Texas
1st Gear Member
Yep, that takes care of that issue.. The 351 piston apparently won't allow enough valve clearance for the MCM.. We do know that the Webcams 101 grind will work with the 351 -http://www.webcamshafts.com/mobile/motorcycle/kawasaki/kawasaki_klx_250_sf_(09-10)_dohc_4v.html - as we have members running it..
Last edited by Klxster; Mar 6, 2016 at 12:53 AM.
Senior Member
Joined: Jun 2013
Posts: 3,315
From: North Texas
1st Gear Member
I have always wanted to know the dyno numbers on a fully modded stock bore - complete exhaust, TM36, webcams 101, lidless (of course)..
BTW, if anyone wants to loan out a properly setup TM36, I'll do a "before and after" dyno test on my bike..
BTW, if anyone wants to loan out a properly setup TM36, I'll do a "before and after" dyno test on my bike..
