So next thread in my series on bringing the klx351 online is this - the bike is stuttering up over 4k rpm and not really making much in the way of noticeable power gains over stock. (i'm in touch with bill, but would still like to hear the experience of the forum).

Is this a fueling/carb tuning issue? Do i need to adjust the mixture screw?

Could it be something else like clutch slippage?

The bike starts easily, idles smoothly, and revs effortlessly when not under load.

 

Need to know what carb and settings first off.

There is a thread recently about fueling a 351. I can only speak for a 330 big bore which should be very similar, I am running 144/1N at ~1000ft above sea level and it pulls like a freight train till 9k at least.

start with the easy things first, change the plug if you havnt recently and do the rectifier ground mod. If you want to check clutch slip, put it in 5th or 6th at low speed and pin it, it will be obvious if its slipping

 

First, let us know all mods from intake to carb to exhaust. If the clutch is slipping, the bike will rev but you won't have any more power to the wheels. It's very noticeable.

 

Once you let us know what carb you are using. The setup in the carb. And details about this issue and when it showed up. Perhaps we can help..

A stuttering/stammering CVK is a badly seated diaphragm and has nothing to do with tuning - it is a owner created malfunction.

 

so a week or so ago i finished up the BB351 build - been breaking it in and adjusting it. Its the Mikuni pumper that Bill supplies with the kit. He stated that the pilot is a 40 and the main is a 140. T-Screw is backed out 1.5 turns. I'm at sea level.

Air box lid is off courtesy of the PO. stock header, FMF Q4 slip on.

Before the big bore it was stock carb with DJ Stage 2 kit.

I did have to take the bowl off of the carburetor during assembly. Initially the pump wasnt getting fluid through the orifice. some compressed air and carb cleaner fixed that (per Bill).

Seems to run better when cold. as it warms up it gets worse (could just be imagining tho).

Need any other info?

 

I'm out - CVK's only.. However, having to clear an internal passageway obstruction with carb cleaner and compressed air means that there may be many more circuits that need the same operation..?

 

@klxster - if you were setting up the stock carb for 351 what would you do - i may bolt it up just for comparison. I think i have a dj132 main in stock (128ish was on there previosuly). what ring would you put the needle clip on to start?

 

I'm running a 40 pilot, a 148 main, and a DJ needle on the 1st clip (top). It's a bit rich in the middle and screams up top. If you're doing a comparison, you may go for a 146 main. The 40 pilot runs great and there's very minimal popping on feel that everyone seems to have.

 

I am waiting on Bryan632s' dyno chart/AFR chart. I only have an opinion to offer on fueling a lidless 351 with the CVK34. With his chart - assuming his AFR is useable data - we can get a better picture...

Until I/we have more information - I would personally fuel my 351 (if I had one) with DJ148/1N, Lidless, with stock slide lift port and stock slide spring - obviously using one of the two DJ needles and a #40 pilot jet. All this being at or near sea level..

 

Bill is not knowledgeable about Lidless fueling. He has always used a KDX snorkel - which is almost as free flowing as the standard DJ stage II (lid on, snorkel removed).. So while I am quite sure his carb would be superior to the CVK if set up correctly, getting the Lidless setup "recipe" for it may be "all on you"..

Certainly sounds like it is malfunctioning at this point - main circuit fueling seems to be faulting.. That is a lot of components and passageways to inspect and "clear"..