PolishMoFo wrote:I was wondering if the polini kit was helpful? I have the big bore kit but have not installed it yet
Since your new, I'll do ya a little courtesy and offer my own take on it. Others will probably have a differing opinion.
So first of all, the BBK is one awesome awesome upgrade, you are gonna LOVE IT!! There are some things though that you should realize and keep in mind though if you want it to run good and run for a long time.
Like I said before, when it comes to the BBK in a Spree, it wants to and it needs to breathe. There is a bit of issue with that though that you will need to contend with.. how much air/fuel to give it and how much you can throw at it.
Now, a couple of the guys here had problems with overheating. They tried doing things like throwing more fuel at it on the main jet with very little success. The problem they were more then likely seeing, is a problem that plagues many people who run it with a pod filter over an air box. Yes you CAN use a pod filter if you choose to do so, keep in mind a free air pod filter will require a jet upgrade a little bigger then what you need with the air box. This goes for about any given motorcycle when people switch to a pod filter. A pod filter, will give you more power, faster revs, more oomph. But it comes with a price. When you don't have that airbox anymore, you eliminate alot of back pressure. What this back pressure does, is help lower your stoich air/fuel ratio. If you can get your stoich down into the 12.0-12.9 range, your engine will be burning the fuel more efficiently and will have fuel to spare to cool the engine. On an air cooled 2 stroke engine, the oil only lubricates, it is your fuel that has the cooling properties. This is important to remember during break in because you don't at this point, want heat to expand your cylinder and what have you too much while the rings are breaking in. The cooler you can keep the engine while the rings and wall of the cylinder find their harmony, the more life and better performance you will get out of your engine in the long run.
So while, yes there are all kinds of ways to go to improve on the performance you get out of the BBK, like doing a better carb, porting the intake, better muffler. Don't worry about that stuff at this point. There are TONS of articles, wiki pages, and very helpful members here that can help you sort that out. I've been going at mine going on over 6 months now.. LOTS of research, and, as you can tell by this thread, LOTS of testing. Keep in mind I spent a ridiculous amount of money. Basically, almost half of last years profit sharing check! That's not the kind of investment I would advise anybody to make unless you are doing a restore project like I am, for the reasons I am. A frugal person can get decent performance out of the BBK and not break the bank, and it starts with breaking it in right.
So with that being said, my advice is use your stock airbox just for now. Don't worry about all these extra goodies you can slap on and try. Drill 6-3/8th inch holes just past the inlet on the air box lid. I don't have a video to show you because I never recorded it because it was not a dyno run, it was an air fuel stoich test. But anyway, the 6 holes turned out to be the very best at letting in air while still maintaining sufficient back pressure. This kept stoich in the mid to upper 12's. Of course, you will not be running the BBK at full horsepower potential like that, but you will not be plagued with heat spikes when you let off the throttle.
A GREAT example of someone whos BBK runs well, is Ultraliner. He uses an airbox with 2-20mm holes drilled in it. I think he said a #90 main jet, and not much else. By volume, his 2-20mm holes are about the same as the 6-3/8ths holes I talked about. The 6 holes are just a tad more volume then what he uses, so somewhere in that range will be perfect for you.
Put a couple hundred miles or so on the BBK with that type of setup, THEN decide if you want to go with a pod filter, or porting or even the Polini. You might be pretty happy with what you have and will want to just keep it as is.
Also, don't let the Dyno run videos I post fool you on the kind of pickup the BBK has. Keep in mind on a Dyno, the Spree has to try pulling a 1,000lb drum off the start just to get up to about 15mph so we can take a reading. Plus I am using higher gears. The dyno starts are NOT representative of how it will accelerate off the start. In the real world, it is much much faster. Especially if you DON'T use higher gears. With just stock gears and a stock carb with a typical #90 jet, the Spree will rocket you up to 35 with a big smile on your face.
And another thing to mention, is DO NOT forget to take an exacto knife or something and trim the boost port on the gasket that comes with the kit. You can find info on this here for reference with an image:
viewtopic.php?f=3&t=33328&p=289752
And last, whatever you do, do NOT beat the heII out of the BBK like I have been doing while it is breaking in. You can get on it a bit, sure, no biggy, who doesn't wanna try out their new BBK and see what that puppy can do? But try not to do it too much. Even with the added stoich boost from the airbox helping keep it cool, a nice steady break in will give you longer life. The BBK is strong and can take alot. Yes, I am changing out mine, but this is only as a precautionary measure and because I am paranoid and partly OCD. I'll leave it to Mr. Jumps to determine if the paranoia was warranted when I pass it off to him to play with. As of today, it starts right up, seems to run great... aside from the experimental pilot issue which doesn't count. A good re-hone and a change of rings, the BBK should be ready for action. And if he figures out where we went wrong on the carb with the pilot swap, this could be a potential savings over buying that Polini. The main thing that made me lean to buying the Polini, is I was getting tired of playing around with the stock carb. I get charged $60 an hour on labor, I work 2 jobs and don't have time to do many things myself, so trying swap after swap on experimental parts just simply isn't in my budget. The advantage of the Polini is I can swap out main and pilot jets by simply buying a multi jet kit.
The issue with the stock carb, is mainly with the pilot jet, as Taz mentioned above, the theory is that too small a pilot causes heat spikes. This problem affects mainly BBK's with pod filter and a bit with ones using an airbox but not as bad. Changing that, is NOT an easy task, Reference this wiki:
http://hondaspree.net/wiki/index.php5?t ... ix_at_idle
On my bike, we attempted the swap to try and address the issue. This was done because we are shooting for that magic 12 stoich number. This swap DOES NOT need to be done to run the BBK well on your own bike. Keep in mind, I'm doing alot of this junk in the name of science... That, and it's fun for both me and the guys at SS Collision & Cycleworks to see how much we can squeeze out of a stock Spree engine. It's something different then the usual motorcycles we each deal with day to day, and it's gonna rock when we finish.
