Spree hopups, starting point

Does your Spree/Elite already run great, and you're trying to make it quicker/faster? Need a monster motor swap? Discuss your ideas here.

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noiseguy
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Spree hopups, starting point

Post by noiseguy »

Edit: Numbers listed below are wrong. Ideas might be on the right track. Read on.

All,

found these on another board. never personally tried them, but here they are. the jetting change, notably, is going to need to be done in conjunction with the manifold and filter change, and probably exhaust as well. the pulley change could be done by itself.

note that if your current scoot is low compression and barely running you need to get the compression up and get it running right b/f you even start messing with the below items. and they could end up blowing a piston/rings. keep an eye on your temps.
-------------------
me, since i did not care if the ped was a wee bit louder i took a 8 inch long 1/4 diameter drill bit and drilled 3 holes length wise into the muffler next to the exhaust nipple.

now if you really feel spunky and what to get the most out of your ped and you have about 40-50 bucks to spend and 4 hours of free time here is what you do.

1. remove the head and have about 60 thousandths shaved off. 20 bucks labor and 6 bucks for a new head gasket. this will increase your compression for more power

2. take a dremel to the intake manifold and open up the restriction, you will see it when you remove the manifold. this will increase air flow, more top end power

3. file about 1/16 inch off the front inside pulley half on the belt drive. this will slightly increase the drive ratio for a higher top end

4. by a size 70 main jet and install it in the carb costs about 6-10 bucks at your local honda dealer. you will need this if go to an after market air filter assembly to insure proper air/fuel ratio

5. by the chrome topped cotton filter element k&n oil breather cap for a chevy v-8. it costs about 12 bucks and it makes a perfect after market air filter. it fits right on the rubber tube that goes to the carb. you will have to remove some off the old air filter assembly though. this combined with the jet gives you more top end power and rpms.

6. drill out the exhaust. the relieves some back pressure for more available power.[/b]
Last edited by noiseguy on Fri Sep 03, 2004 9:13 pm, edited 2 times in total.
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Post by noiseguy »

I am starting through these mods on my scooter. first off, the inner pulley needs .030" taken off the inside, not 1/16". any more than that and you will be running the belt outside the pulley. as for the head, it looks like you could take a max of .030" off the head before you lose minimum piston to head clearance of .010". i am going to start with taking off .020".
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Post by noiseguy »

I ended up milling about .017" off the head. This pulled the piston/head clearance down to .028" all the way around. Stock running clearance is .045". All the measurements are +/- .001; the piston top has a grained surface and is hard to get a good measure on. I'm using electrical solder to measure the final clearance.

The impact was that the scooter starts a lot easier. I need to measure final compression but it should have increase compression from 7:1 to 7.5:1. Not exactly huge.

This and the pulley mod did nothing for top speed. It's still running at 29 MPH tops. I'm going to respace the pulley out to see if I've made it quicker to 29.

BTW, did I mention this is an '84 Iowa version? Not the best to start with in the first place. Exhaust has been derestricted, but I think I may open it up and pull the baffles, using the exhaust can as an expansion chamber only. Anyone already try this?

Also, if you look at the service manual, the Iowa version has different, later exhaust and scavenge timing than the regular version. Looks like the barrel is milled to a slightly different height than the base model. If you look inside the barrel, you can see that the piston doesn't even completely uncover the exhaust port at BDC. A new base gasket might fix this; with the removed head material I have .017" to increase the barrel height before I need to machine the top of the barrel.
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Post by noiseguy »

BTW, a word on head to piston clearance:

I have no idea what minimum head to piston clearance can be run. If you talk with guys that work on KZ1000s, which were a roller crank and piston pin engine, the minimum clearance was .040". Any smaller and the piston would smack the head. On mopedarmy.com, I've seen ppl talk about .010" minimum clearance. Scary close. Most guys messing with these engines will deck .020" initially as a starting point, which is what I did. Right now it seems to be fine; time will tell.

I'd be interesting in hearing anything that anyone had to say about this subject.
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Post by Jim »

Did you do every step? Including the air filter adaption and the jet increase? and still no improvment?
86 Honda Spree - Lawn Ornament
83 Suzuki GS450E - Sold
92 Honda CBR600 F2 - Current Daily driver
Spree Repair Guide
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Post by noiseguy »

After looking at the engine more closely, it's obvious that the original poster (whoever it was) either didn't know what he was talking about, or was very careless in listing his numbers. You'd smack the piston into the head, even slowly rotated by hand, if you took .060" off the head. And taking .0625" off the pulley would have the belt running on the meat rather than the "belt," which I think will wear the belt out pretty quickly... I need to research that last bit more.

I'm working through things in the order they make sense to me. Messing with the jetting and inlet side will be the last stuff I try, since jetting doesn't matter if you don't improve airflow through the engine. Inlet is tricky. Try disconnecting the carb to filter tube at the carb. The Spree will start, but won't accellerate past 10 MPH. I tried it to verify what Jerry had said.

Exhaust will be next, if I don't decide to try bumping up the port timing this weekend. The jetting has to be done to balance the exhaust as much as the intake. Basically you don't want the engine to lean out and burn a ring/piston.

Bumping up the compression should have increased HP a bit, and shouldn't require any rejetting to work. Messing with the pulley should have increased top speed more than it did. I need to measure the ratios and check compression to see if I got the improvement I thought I would.

At this point I'm posting this more as a journal than anything. I'll also post when I either A) blow up the engine B) get something that's a genuine improvement. At this point I have neither.
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Post by noiseguy »

Went back and checked the numbers. The combination of pulley and slight compression bump got me about 3 MPH increase, from 27 to 30 on an '84 Iowa spree.
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Post by Kikwear »

Did you run a higher octance with the increased compression? Any gains alone with the higher CR? Would any carb/exhaust mods be needed for CR increase? Only reason I ask is because I have the head off and could try this.

I don't understand the pulley modification at all.
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Post by noiseguy »

Look at the pics from the service manual for the pulley mod. I will eventually post pics, but not anytime soon. You would be shaving the inner pulley face (closer to the piston.)

At 130 PSI, high octane is not required, but I run it anyway, even on an unmodded version.
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Post by Kikwear »

What I was trying to ask earlier that I didn't make too clear was this; if I just shave the head 0.20", will I need to perform any other modifications, intake or exhaust wise? You said it started better but no performance increase?
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Post by noiseguy »

Increasing compression works by itself to increase efficiency and power. No other mods are required, however it will make any other mods work better. I would use electrical solder to check piston to head clearance before doing any shaving. I tried to maintain a .020 head to piston static clearance. You also may want to pick up a spare head to use. I bought one on Ebay for $5 a few weeks back in order to allow me to reverse the change.

I've been slack on this project lately. I need to get my expansion chamber built up and try it as well.

In retrospect, I'd try the pulley mod before messing with anything else, as I'm sure that works to increase top speed.

I also picked up a spare intake runner, which I clearanced out. The carb to intake manifold does indeed have a restriction, which you can see if you pull it apart. This restriction is in the way the intake has been bored after casting. I used a set of inexpensive riffer files (small curved files) to smooth and enlarge this transition. Took about an hour. Haven't tried it yet; if it does anything I'll post pics of the mod.

The principal behind the intake tract is that you have one choke point, at the carb. The intake manifold restriction descibed above creates a second choke point in the flow, which is not exactly the way things should be. You want even expansion after the carb. That said, I still don't know if it will help, as you cannot completely remove the restriction without removing too much material. The intake still needs to mechanically support the carb, after all.
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Post by Jamie_Miles »

Your actually going to loose power running high octane gas.

There is not nearly enough compression for it.

The octane rateing stands for how slowly the gas burns. The lower the octane rateing the quicker it burns.

Higher octane is for higher compression engines, to prevent predetination.
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Post by vette76 »

I also picked up a spare intake runner, which I clearanced out. The carb to intake manifold does indeed have a restriction, which you can see if you pull it apart. This restriction is in the way the intake has been bored after casting. I used a set of inexpensive riffer files (small curved files) to smooth and enlarge this transition. Took about an hour. Haven't tried it yet; if it does anything I'll post pics of the mod.

The principal behind the intake tract is that you have one choke point, at the carb. The intake manifold restriction descibed above creates a second choke point in the flow, which is not exactly the way things should be. You want even expansion after the carb. That said, I still don't know if it will help, as you cannot completely remove the restriction without removing too much material. The intake still needs to mechanically support the carb, after all.[/quote]



did you ever try it after you removed the restriction from the intake? can you post a picture of what you removed if it is not too much trouble? thanks.[/quote]
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Post by vette76 »

Looks like the barrel is milled to a slightly different height than the base model. If you look inside the barrel, you can see that the piston doesn't even completely uncover the exhaust port at BDC.



is this true on regular models too? that the piston does not uncover the port? if i bor this port will it be faster?
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Post by noiseguy »

I checked again, the piston hit BDC at exactly the bottom of the port, as it should.

No offense, but don't start grinding your ports unless you know what you're doing. Port timing is a big deal on 2-strokes, similar to cams on 4-strokes and every bit as fickle. I'm not touching mine.

For more info, go here. This will get you started:

http://www.macdizzy.com/cyl_primer.htm
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