Why is 86-87 Spree faster than 84-85?

[Meatball]

Is it because the 84-85 Spree has a dished piston and 86-87 is domed? Can a domed rebuild kit fit on an 84-85 and expect to see the same speeds as an 86-87? Im thinking of putting a fresh top-end on my 85' and all the rebuild kits I see on Ebay have domed pistons. Cant find a dished kit anywhere.

[eclark5483]

84-85 has a 12T gear while the 86-87 had a 13T. Iowa Sprees, all years, also had the 12T.

http://hondaspree.net/wiki/index.php5?t ... ion_Ratios

Other differences depending on model were muffler and carb jet. If your by chance looking for a 13T gear I have one available. I know you just recently did a swap for Taz gears (as did I), but I actually picked up a 13T a while back as I was originally intending to swap out my Iowa Spree's 12T for one, till I changed my mind and went with the Taz gears instead.

[Meatball]

Im just looking for a fresh stock bore rebuild (41mm) for the 85' and was wondering if the domed kits Im seeing for sale on Ebay will fit. I know my factory piston is dished. Im gonna run the Taz gears since they give me close to the speeds I need to buzz around town. It would be ideal if his 48mm bbk would be happy in my motor but I just cant get them dialed in right no matter what I try. Im looking for reliability since I go on long rides at times and cant be constantly worrying about temps.

[noiseguy]

There are also differences in the head design, and I suspect the porting. Decreasing your squish clearance from piston to head is one of the most effective ways to increase power on these engines.

[Meatball]

Am I able to reduce squish myself? By carefully using a dremel and taking a bit of the edge off the ring of the head?

[noiseguy]

Am I able to reduce squish myself? By carefully using a dremel and taking a bit of the edge off the ring of the head?

To a 0.001" surface tolerance with a dremel? God no.

You need a machine lathe or mill to do it right. Head can be turned down on lathe using the spark plug threads as a holder.

[Meatball]

I wonder how much a head shop would charge for a quick mill?...hmm

[Ultraliner]

I would imagine getting 0.001" fly milled off a small scooter cylinder head wouldn't set you back too much

[jerz40]

While you are at it, you may want to swap out the reed valves on your 85 and put on one from a 86-87 spree. As the ports or whatever you call em are much bigger on the 86-87 sprees. I swapped my 84 sprees reed valve out and have noticed better speed than most 84-85's with the 86-87 reed valve. They talk about it this somewhere here on the forum, that's where I found out. For the piston, just buy one of Taz's rebuild kit's for $23, he was selling them on eBay, not sure if he still is, but they fit all spree years and are very good quality. Good Luck!

[noiseguy]

I would imagine getting 0.001" fly milled off a small scooter cylinder head wouldn't set you back too much

On an unmodified head, you can remove up to 0.020", or the thickness of the head gasket, safely. Assume Honda did this so if you forgot head gasket it wouldn't crash head. This assumes matching piston and head, not a mix of late domed piston with early head, which is another combination that increases compression.

You can verify head to piston clearance with lead solder by installing new head, loop solder through plug hole, rotate engine by hand, measure results with micrometer. You want a cold running clearance of >0.020". Last one I did was 0.025" or so and ran fine. At some point smaller you'll crash the head... I've never seen a reliable published number for this clearance, just anecdotes.

[Meatball]

Been reading up on squish and how it works. This Handbook is somewhat prehistoric and printed 40+ yrs ago but has amazing information. Im looking at page 51 of the pdf file but actual page 41 in the book. Jennings knows his stuff.

http://amrca.com/tech/tuners.pdf

[Ultraliner]

This is true jerz, another thing to do is install the intake pipe and reed block off an SB50(maybe the same as the '86 - '87?). This was the first upgrade my Nifty got and the increase in pull and top end was actually noticeable

Have some comparison pics somewhere if y'all interested

[jerz40]

Oh yes that's right! I think I have some SB50 reeds and intakes, I'm thinking I'm gonna haft to do this modification on my spree. But, my other 86 Beater Spree I put in a CDI box from a Aero 125, I literally with the wind to my back hit 40mph, no joke! And it's all stock with no modifications! Just a different CDI! Those CDI's have restrictions in em too

[jakubman1]

So can I exchange my piston,reeds, and gear for more speed ??

Is changing the inake better than the 85 model?
I have a full 86 donor bike with everything still on it 3600 miles. Pretty rusty but I took the head off with the piston and jug and lubed it with some PB blast. Looks pretty good. But I can tell someone used cheap oil lol I sanded the top of piston too. Someone let me know what else I can exchange for more stock performance

Ill post some pics soon

[jerz40]

I believe so, I have had a lot of experience with these bikes and on my 84 spree, changing the reeds to 86 and putting a rebuild kit in with a domed piston head gets me to 30mph easily, when I change the CDI out I hit 35mph on a 84 SPREE! And you are correct, 84-85 sprees are slower than 86-87 sprees, this is why I always ride my 86 sprees because they are much faster, but you can make the earlier model years faster too with a few mods like I mentioned. Also I've noticed too a larger rear tire helps ALOT! Go with a 2.75-10 and leave the front tire 2.50-10, you'll notice a difference!