Spree bbk issues.

[Meatball]

The scars in my seized piston is isolated to only one spot. All on the back side opposite the exhaust manifold. Yes, the gasket was trimmed to match the jug AND the top of the crankcase. I noticed after I trimmed the gasket's boost port to match the jug openings, I placed the gasket on the crankcase and saw there was some additional trimming that was needed. Even after a FULLY trimmed gasket and absolutely ZERO gasket material causing obstruction...still seized up on the boost port side. Rest of the piston was smooth and breaking-in nicely. It was lubed all around the piston when I pulled it except where the scars were. It was bone dry in that spot. Could there be a lube issue?

[Peteyparado]

What was your compression ?? An your jet size looked super lean an hug comp.. Don't have to be at WOT TO SOFT SEIZE..

[jakubman1]

Well Ya know I did install the.dang jet that came with the kit.

[jakubman1]

I dunno what the compression was. If it runs it's got compression lol
Man do I miss my little piston. I.think I may put it back in. Is there a way to clean off the carbon build up on a piston head? Or just leave it alone
I think jetting should.be 100-105 on the bbk. The.kit.comes with an 87. Stock I think is 68

[eclark5483]

600 grit sanding wheel will take that right off. Would recommend doing it on a lathe though. Go 600 or even 1500 which might take a couple pads, should give you a nice smooth surface without digging into the piston itself. Your just looking to remove the carbon, not shave the piston. If you want to be real gentle, use a buffing wheel with some finesse compound. 1500 grit in a lathe plus buffing wheel with finesse compound will give you a mirror finish piston.

[Meatball]

OK, dudes. I've been doing research and I found out what some of you guys have already known but is new to me. Every different lean/rich adjustment that can be made only changes certain throttle ranges. One adjustment only deals with idle to 1/4th throttle, another deals with 1/4 to 3/4 throttle and another deals with WOT only. So, just because the mixture may be set perfect at idle doesn't mean its good at 1/2 throttle or WOT. This makes sense since jakubman seized his at WOT once and I seized mine at 1/2 throttle. Possibly the adjustments were off on each of our bikes for that throttle range. Plug chops cant be done on Sprees since we cant take them out of gear when we kill the engine.

I know this is an old posting and the bikes/carbs they are discussing aren't exactly for a Spree but read the posts from "crusty" and "big fella". They explain a few things about adjustments that I never knew. http://www.dirtbikeworld.net/forum/arch ... -2463.html

Feedback on this topic would be appreciated.

[jakubman1]

I think we just need to buy the UNI filter. Thats it....

Meatball your still using the airbox with holes right??

Get rid of the pipe that connects and install the uni filter.

[Meatball]

I truly believe our issues run deeper than improper airflow. That may be a contributing factor but at different throttle positions other adjustments need to be corrected. Im beginning to think the 87 jet supplied with the kit is a good starting point but may not be ideal for every application. The jet affects air/fuel delivery during 1/2 to WOT so that MAY be where ONE of our problems lie. Im sure that once the air/fuel is adjusted properly at EVERY throttle position, this bbk will sing better than Whitney Houston before Bobby coked her up.

[jakubman1]

If i can just find out which UNI single layer i need lol

[jakubman1]

http://shop.unifilter.com/p/single-stag ... 0%9D?pp=24

THIS

[jakubman1]

I think it makes sense. Cause more air with bigger jet will give you more gas. You need more air for.that jet to push the gas through ??

I think that's the problem here.
If you use the stock air box at all your restricted the bigger jet to a degree where it'll run lean regardless.

[benji]

Actually, that's the opposite of my understanding. Too much free flowing air and the carb won't have enough vacuum to suck fuel out the bowl thru the jet. That's why you need a bigger jet w uni filters and sports mufflers- more airflow means less vacuum. The oem airbox provides that vacuum while also providing a reservoir of clean air waiting to be sucked in the carb. When the slide is open that air is used up and more air is flowing into the box.

[benji]

If $0.18 worth of foam was better than cad engineered air boxes (on modern cars-probably not cad engineered on our scoots haha) Then I think Honda-san would of made the change years ago.


Of course, I'm running a uni filter too, but I don't really have a choice w a pwk carb. But, I'm using a bell mouth which helps create vacuum on filterless set-ups.

[Wheelman-111]

Greetings:

"Better" is a question of perspective. Honda must comply with EPA noise and Hydrocarbon emissions laws, and an open pod means the vehicle fails. The box is a HUUGE quieter-downer. I learned this when I unscrewed the cover with the engine running - the intake noise is Way louder than the stock or even the PG short pipe.

Modern 4-stroke airboxes are "Tuned" like good 2-stroke exhausts so that the pressure waves are timed to stuff the maximum amount of air into the combustion chamber before the intake valve closes. This minimizes the performance loss, and might even increase power at specified RPMs. But because Honda's AF series engines' intake tract is so long and convoluted, blowing in from the left side of the crankshaft, the airbox isn't as great a performance enhancer - or detractor, for that matter. What is important, as Benji pointed out, is that the inlet holes to the airbox are smaller than the carb throat diameter. That negative pressure pulls more fuel up the small-ish jets. Without the box, the jets flow less fuel for any given RPM, but especially less at higher engine speeds. This leans the mixture, particularly the fixed jet Pilot circuit.

[jakubman1]

So are your telling me that this air filter I just ordered is going to run my engine even leaner ????

Somethings wrong here cause Taz and Pat both said that the uni filter is needed for the spree bbk to work properly. I don't believe that they would tell me a fib.

Now I'm confused as *.