Just ordered my BB351, I've been told it ships in the new few days. Should have everything built up next weekend. I found a place in Calgary that does Dyno testing on motorcycles with good reviews. I will be sure to document my findings here.

I see a lot of discussion involving carb tuning with the big bore, how does my base starting point sound?

Elevation:3000-3500ft ASL
Needle: DN0228 @ 2N
PilotJet:38
MainJet:134
Airbox:Lidless
DG-O pipe with stock header

Ive never been to a Dyno test.
After reading the forums, ive been told to arm up with knowledge and specific goals at the Dyno test, what type of test should I be performing? Any tips?

Geoff

 

It boils down to telling them you want your DRF files on your thumb drive. They either view the data files, created off your bike, as yours or theirs - so they'll do it or not..
The data files are the whole enchilada..

 

I have another post on the subject you've probably read through. Right now I'm running 140 main, needle on the 3rd notch. It runs fantastic, but goes a but flat at 7000rpm. Also running a 140 pilot with great results down low. Bottom end power is absolutely perfect. That may be a good starting point to follow. In waiting on my jets to come in to go up to a 146, 148, or 150 before I take it to a dyno. When I reject, ill stop by to let you know how it runs.

 

Well I know the CVK34 but I don't know 351+lidless fueling recipes using a CVK34.. I'll do the best I can for you..
Lets assume your carb is assembled correctly and functioning correctly.

Correctly fueled low and mid (under 6.5-7K) produces very strong throttle response and acceleration - generally a lower clip setting with a somewhat small main jet, or a higher clip setting with a somewhat large main jet will provide exactly the same fueling below 7k.

6.5K-7k and up is "main jet only fueling". If the main jet is incorrectly sized, the top end suffers. When correctly sized, the top end makes so much power that it's hard to put into words..

This is why CVK tuning must start with 7k and up analysis in order to find the correct main jet. Then idle-7K can be tweaked with the needle selection, spring selection, and the clip setting.

I would say the DJ140 with that low clip setting of 3N is fueling the low-mid well, only to have the top end fall on its' face because the DJ140 is not correct.

If I ever go 351, it will start off with DJ148/1N lidless with stock spring and stock lift hole. BTW, DJ150/1N runs a KLX250 perfectly fine. But the dyno showed a power loss below 7K due to an overly rich AFR..

 

Incredible. In 2017 U.S. KLX250S riders are still talking about carbs and jets. It's cool in its simplicity and all, but talk about a throwback! On a side note, I'm looking to sell an KLX250S OEM cylinder, cams and CVK34 if there's an interest in such things...Am I posting this in the right place?

 

Yeah, but the interesting part from pure function is...

• no electric fuel pump that could fail
• no high dollar black box computer should that go bad
• no high dollar computer modifier for high performance hop up
• various carb sizes that both Keihin and Mikuni are still pumping out, try swapping out EFI for a larger one.
• less than $100 to change the fuel mix with inexpensive brass bits

Admitted the electronics failures would be rare, but once jetting is right it will not really break. Maybe old gas can be an issue, but not a big one. You see, there are advantages and disadvantages to everything. The reason carbs were still on a number of bikes was cost and EFI wasn't needed yet to meet emissions. Heck Honda even still had a carb on the 2016 CRF250X - and it got good review on how well the bike carbureted in Dirt Rider. So archaic, maybe. But functional when dialed in, for sure.

$150 for a TM36-68, how much for the electronics to increase performance with EFI?

I tend not to do technology for technology's sake, but for function. I still have Windows7 because I don't need 10. I don't have the latest iphone because I don't need it. I use relatively new technology in my classes and some other personal use, but am not into overkill. I'd rather have classes doing rapid prototyping with a laser or a small mill than a 3d printer, because the affordable printer for classroom use is too slow for every student to do a project - it isn't the equipment, it is the purpose. Same with the bike.

You see the reason I have a carbureted bike is because it was only $2000 and has pretty good equipment/performance for the class. The Honda is heavy and a lesser performer with lesser suspension and the WR is just too much money for what it adds in performance. So carbureted it is... the $150 flat slide is waiting in the garage to be installed.


FWIW, I still wear Converse All-Star Chuck Taylors and wear vintage Shuron Rensor ZYL glasses (still making 'em since 1952) as well as some other throwback type frames that make a statement. I even wear regular jeans without prewash, abrasion, or cuts to create a look. Mine have patina, because it's real. They wore that way.