Carb for a big bore spree

[mkluvin]

1984spree..... had damage to the cylinder and piston (i know its hard to believe)I just bought a big bore kit from taz .. should be here soon . I have the stock carb with the stock jet, has any one found the right jet size as I've heard many speculations on this matter. This carb will have to get me by for a few months till I get a bit of cash. I would like to end up with a nice oko so I don't have to frog around with the stock airbox . this leads to the next question what mm of carb 24? 28? im not looking to race. I would however hope to see 40 mph (the wife has a stock honda express. so if i go too fast I'll have to build her's too!) I also plan to go with a 1/2 x24 belt. I was told this will help the top but hurt the low end, but the big bore should help. I have no plans for a pipe upgrade for now. but if any one knows (or can link me to exhaust improvements that will not break the bank that would be cool.. thanks so much


now before I get hit with the "read" and "do your research" gripe , I would like you to know that this forum is so jam packed with d*** good info that sometimes there can be conflict with no consensus.

so the factors are:
1984 spree
44mm big bore
1/2x24 belt

the variables:
jet size for stock carb
mm size of oko carb (24-28) and oko jet(buy the large or small 10 pack)

[Wheelman-111]

Greetings:

There may be much discussion as to how much carb it will take to feed the Tazland bore's modest appetite for fossil fuel, but this is certain:

Whatever carb you procure will need to be tied into the case port somehow. Most aftermarket big carbs use a 31mm spigot mount that clamps into an aftermarket intake/reedblock assembly, the "CT" being a very popular version. The Spree 2-bolt intake manifold/reed mounting isn't compatible with any of these.

NoiseGuy was selling a slightly bigger SB50 case reed assembly, which may be a worthwhile upgrade if you're trying to go bigger on the intake side. People have reported using the Tazland-supplied jet (a #95) and Honda's own 78, and lots in between. I haven't read any hard results, but I speculate that 78-82 would be about right for the stock carb.

Arreche carbs sold at Scooter-Center.com use the same flange-mount and bolt spacing as Honda. There is a very good 17.5mm that had enough CFM to feed 65cc Flash I to beyond 55 MPH, so that may plenty for the big-bore Spree as well. The Arreche uses the stock bystarter and connections. Fitment of the stock airbox may be possible; the carb is dimensionally similar to the stock Keihin. However it does feature replaceable pilot jets, and that may open up different air filter options. There are different needles and emulsion tubes as well for lots of Tuning (and tuning error) Opportunities. The carb bellmouth fits 1" filter donuts. Search Honda "Vision" on the ScooterCenter.com site. Unless you're fluent in German, click on the Union Jack flag.

As you enlarge the intake side, the Spree's limiting factors shift elsewhere. The pipe is an almost certain barrier to high (power-producing) RPM. If you enlarge the pipe, then the small transfer and boost ports emerge as an issue. One thing's for sure: You can't assume world-beating power just by throwing on a big carb.

Please let the Forum know your decisions and outcome?

[mkluvin]

I'll will be sure to keep you up to date on the progress!

I'm in the "the less day to day tweaking the better camp" this all came about because like so many others, the the piston pin clip ring gave out and toasted my cylinder.. the dealership in my area is over 200$ for the repair parts. so taz's kit seems the better option.

with the little more power I'll gain and a bigger belt(1/2x24) to use up the said power. do you see any reason what I should have a problem reaching 35(speed limit on 95% of the roads where I live)with the stock carb and correct jet assuming I can tune it in?

[mkluvin]

well the big bore is on and the bike is as most have found not to be taking to well to the increase from the stock 65 jet to the 95 shipped with the big bore otherwise I was very impressed with the kit. Anyone know where i can get a better match my local Honda shop told me they were discontinued.

[Bear45-70]

well the big bore is on and the bike is as most have found not to be taking to well to the increase from the stock 65 jet to the 95 shipped with the big bore otherwise I was very impressed with the kit. Anyone know where i can get a better match my local Honda shop told me they were discontinued.

What is discontinued? The carb or a jet bigger than your 65. I just ordered a 75 jet fom my dealer.

[mkluvin]

thanks bear. Ill try other dealership in town. do you think a 75 -78 would due?
im using the stock airbox but i'll mod some holes in it .

[Bear45-70]

thanks bear. Ill try other dealership in town. do you think a 75 -78 would due?
im using the stock airbox but i'll mod some holes in it .

It is a place to start, but I would think a 72 would be close but every engine is an individual, so starting little rich would be better that a over rich 95. Get wheelman to take a guess at what you need. He has a lot of experience.

FYI Honda jet numbers;

Part Number 99101-393-0XX0 with your jet size in the ÔÇ£XXÔÇØ.

Alternate Part Number 99101-187-0XX0.

A 78 jet would be # 99101-393-0780 or 99101-187-0780

Not all jet numbers are available but I know 68,70,72 and 75 are available.

[Wheelman-111]

Greetings:

Thanks for the undeserved compliment, but I have no experience with 58cc Sprees. Just a HAG, but I'd start with an 85 which should be rich if anything, and test, test, test. 95 sounds like crazy talk rat thar!

[Bear45-70]

Greetings:

Thanks for the undeserved compliment, but I have no experience with 58cc Sprees. Just a HAG, but I'd start with an 85 which should be rich if anything, and test, test, test. 95 sounds like crazy talk rat thar!

I can agree with that.

On another note, I THINK that unless mkluvin is carb knowledgeable already or willing to "go to school on carbs and jetting" that staying with the stock carb is a better route than the aftermarket carb route.

[mkluvin]

I'm with you on my skill and stock. really just want to bring this dog back to life and have a solid bike. and the big bore was the economical way to go.

thanks for the great jet info I ordered jets today a 78 and a 85 so now I have a 65 68 78 85 and 95 that should be enough to come close i would think I also have an old air box cover I'm gonna drill holes in the top and adjust with a grill vent between the jets and air I should come out ok. and of course I will post the outcome.

[noiseguy]

A 95 Jet would be a good start for a pod filter.

Frankly, with the stock air filter in place, the 68 jet will probably work best. The big bore will just pull more of the atomized fuel in at the right Air/Fuel mixure.

A bigger issue I see is that the stock oil pump will need to be augmented with some 60:1 premix.

I still have the SB50 intake and reeds. Those would make a nice upgrade, esp. for a big bore bike.

[Wheelman-111]

Greetings:

Quoth NoiseGuy:

A bigger issue I see is that the stock oil pump will need to be augmented with some 60:1 premix.

I still have the SB50 intake and reeds. Those would make a nice upgrade, esp. for a big bore bike.

I agree with this completely.

A 95 Jet would be a good start for a pod filter.

You can try it, but I doubt it'll even run.

Frankly, with the stock air filter in place, the 68 jet will probably work best. The big bore will just pull more of the atomized fuel in at the right Air/Fuel mixure.

Had you asked me 8 years ago, I might have agreed. I posed the same question regarding a big-bore conversion for an 883cc Sporster to a 1200. The conversion consists of reverse-dome pistons (to manage the compression increase), bigger HD or bored-out stock jugs, ( the pistons are a full half-inch bigger...) and a larger main jet.

The reason the larger main jet is mandatory is that the jet is flow-limited by the size of that tiny hole, regardless of the degree of vacuum pressure change across the venturi. You'd think that the greater volume flow of air would draw a proportionately larger quantity of fuel, but the fact is that increase in fuel flow doesn't match the incoming air. Stock for 883s in the early 2000s was 150-160. the 1200 needed 180-185, or a fried bore was the inevitable result.

Similarly, a 20% increase in Spree displacement must be accompanied by a larger main in your Spree, even if the stock intake tract is retained. I think 95 was by Tazland on the presumption that the user would use a pod, for sure. It might not be too big if you manage to cobble up a pipe of some sort, but sure sounds big for the stock exhaust.

Submittted with the benefit of a complete lack of Spreexperience...

[noiseguy]

Interesting. I learned something new today.

So on the Sportster, a 30% increase in displacement = 20% increase in jet size.

So for a 10% increase in displacement, 7% increase in jetting. That's a 68 --> 72 or so.

Sound close?

[mkluvin]

was the sportster a 2 stroke and does it make a diff?

[Bear45-70]

was the sportster a 2 stroke and does it make a diff?

Harley's Sportsters are all 4 strokes and you are right, it makes a big difference.