K&B .67 fuel delivery problem

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Hank

Member
Joined
Apr 8, 2002
Messages
5
K&B .67 fuel delivery problem

Am having a problem getting a consistant fuel flow to my .67 outboard. It's still in the break-in period, so I'm running it rich, and at moderate but varying speeds. It seems to have the most trouble accelerating after decelerating for a turn. Pickup is located stbd aft in the tank, so air is (so far) not an issue.

I did notice one thing. There is an air gap of approx .018" between the exhaust adapter and gearcase surfaces. It does leak out exhaust, so this may cause a lack of exhaust pressure. Is this gap supposed to be there? Doesn't look like it should, but you know how it is when you're just starting out in RC.

Also, how much deflection is normal for the prop shaft? It's gotten a little loose, and I wanna keep it decently balanced. Yes, the brass prop was balanced well on a magnetic balancer.

I know these are really basic Q's, but you gotta start somewhere in this sport. :- Thanks in advance for replies!
 
Re:K&B .67 fuel delivery problem

Hi Hank!

Are you sure you are running it rich? Sounds like you're lean? Did you know you only have to break in this engines for about 10 to 15 minutes?

Is your fuel tank as high as possible?

I will put my new .67 K&B running for the first time this weekend. I'll keep you informed about my findings. Do you have the new style carberettor with the seperated needle?

I will place the whole story of making this boat on my site. I have a Schink cat (Germany) to keep this engine on the water. What kind off hull do you have?
 
Re:K&B .67 fuel delivery problem

The gap is typical of all K&B outboard motors except the SS versions. I don't know why they did this, but if you want, it can be sealed with an O-ring
 
Re:K&B .67 fuel delivery problem

If your having problems accelerating after decelerating then you might have a mid-range adjustment problem. If you using the old style carb with the black needle and brass barrel and o-rings around the mid-range screw then open or close the slotted screw and try it. You could be rich in the mid-range and it takes a bit to clear out or lean and it sags when you open the throttle. If you have the new style carb with the big low speed dial then adjust it either way. Check the slot in the barrel for obstructions as well as they can clog. Take the carb off and the slots must be toward the engine. Hope this helps...
 
May have found the problem!

Thanks for the replies, all. This little DPI tunnel is gonna get the full correction treatment.

It's amazing what you miss when you're looking right at it. Looks like the previous owner used a Dremel tool to open up the rear exhaust outlet in the gearcase. They did a nice neat job, but destroyed the proper function. Not enough exhaust back pressure here. Looks like it's gearcase time.

This .67 does have the old style carb with main needle portside. Once the gearcase gets changed out, the mixture should adjust normally.

Am I the only one to run across oddball problems like this? If I weren't bald, I'd pull my hair out!
 
Re:K&B .67 fuel delivery problem

oddball problems?

I was at the lake last weekend. I tried to start the engine. Even with priming of the engine (full throttle and the top of my finger on the carb, no plug) it did not pull fuel at all. At home again when I was taking apart the same sort of carb from my .45 ob I mentioned one thing:

when looking into the carb from the engine side I saw a small hole in the spraybar which opened when opening the throttle. Then I looked at my .60 carb and guess what. I saw the same slot. But then looking from the outside.......

I that what you mean by a oddball problem? anyway I'm having a go next weekend. Hope it works better then.

I checked my engine for the gap you talked about. Did not find any. Is it possible that this is removed on any of the new engine's?
 
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