85 Spree, test bed for mods

[keithw]

I didn't torch it out. I had soaked this one in Drano (lye). The carbon left washed out with the hose.

Took it out for some runs this morning. Here is the plot.



Pretty much the same as the drilled muffler except the top end is a bit lower. It topped out at 25 mph and 8000 rpm. Just what a stock one should do. Only a couple mph less than the drilled one.

Pulled the cover off the hole in the side of the muffler. It was louder but it was more of a mellow sound, less raspy than the drilled baffle. The top end was abut the same as the drilled one. I'm going to put a bigger main jet in and see if that helps any. Given the less raspy sound and the ease or returning to stock I like the hole in the side.

I've ported out my spare intake manifold. After fiddling with jeting and the open muffler I'll try it out.

keithw

[noiseguy]

'85 Spree topping out at 25-26MPH sounds about right. Let us know what the stock jet is (both #65 and #68 were used). My experience has been that upjetting doesn't do anything unless the filter side has been modified.

You drilled the hole right through the federal noise mandate tag... make a nice flat spot to cover over.

[keithw]

The jet currently in there is a 68. I'll try a 70 and see what happens. Yep, right through the tag. On the inside the same distance back would be a little less obvious.

keithw

[keithw]

Ported out the intake manifold.

Before:





After about 20 minutes with the Dremal/dye grinder:





Did speed runs and found something interesting. This is with the exhaust open and a 68 main jet. A 70 main is too rich. The main part of the curve is about the same but the top end it higher. After it hit the 27 top end like last time the speed kept creeping up very slowly. Ended up just over 30 at about 9500 rpm. It will do 30 but the top end isn't real useful. I'd really like to see more area under the curve. That's what will allow it to push a higher drive ratio.



Are these mods usefull? Absolutely. Will they turn your Spree into a rocket? No. Given that they were basically free they are a good return on your investment.

I think the next step will be milling the head. I'll go with the reccomended .020".

After that I'll look into pulley mods. If I can't get more area under the curve the acceleration will be reduced but I should be able to raise the top end.

keithw

[keithw]

Popped the head off and installed a .020" shaved one. The piston is the dished one (puke). The shaved head will push up the compression ratio and hopefully add a bit more power. It will be Monday before I can take it out for speed runs. When I get to installing a ported cylinder I will also go to the domed piston.

keithw

[keithw]

Did some speed runs with the shaved head. Picked up a little power. The top RPM was about 10,000. Interesting thing. At about 9,000 it started to pick up speed. I suspect it is starting to run lean as it started soft siezing about 10,000. This is consistant with reports of derestricted engines running great untill they cook. This is with a 68 main jet. A 70 is too rich below 8,000.



This is the the runs with a shaved head, drilled exhaust and smoothed intake manifold. Still a few more thngs to try.

keithw

[keithw]

Moving into dangerous territory. If you don't understand carb jetting just go on to the next post and don't even read this one. If you burn up your motor go cry to someone else.

Pulled the cover off the air box. It was so lean it just about wouldn't run, no big surprise. Kept stepping up the main jet. I've got a 90 in it now, up from the 68 stock one. It is a little rich but my 85 is in the Pal. Need to order another 85, part number 99101-1870850. Will your Spree need an 85 if you remove the air box cover? I don't know, jets aren't that expensive, buy a few different ones and see what your bike wants. Once I get another 85 I'll do some speed runs. With any luck my head temp gauge will be here by then also.

If you have been paying any attention at all to this forum you will know that running without the airbox lid is asking for big trouble. I am trying it to document the hazards and benefits, if any. If you want to try it and you burn up your engine you will need to man up and not cry about it.

keithw

[Kenny_McCormic]

Im thinking you need a richer pilot, put the airscrew all the way in.

[keithw]

Thanks for the input. The low speed seems fine. I did need to adjust the air screw. When I first took the cover off it would idle fine but at about 10 mph it would just stop running. As I stepped up through the main jet sizes the speed where it cut off kept going up. At 80 it was just struggling a little bit, still lean but almost there. My 85 is in the Pal so I went to the 90. This four strokes at the top end, about 25 mph. It is interesting that the Pal with the air box derestricted also needs an 85 main jet. I am really interested to see what the plot is like when I get the 85 in it. That jet should be here in about a week.

keithw

[burnt_toast]

hmm so are you going to run with an open filter now? from all experiances past, there is virtually no gains from that on a near stock setup albeit your tweaks. I'd like to see what your plot ends up like though.

Have you tried going to a colder plug too? Maybe richen the needle one clip as well? Don't recall if the spree needle is adjustable, but I would try that while staying with the 68 main and stoxk box. Or go with 70main and try small holes on outside of air box till you have a good balance overall. Maybe also keep 70main but lean the needle and/or pilot to compensate since its rich in that range.

Just things to try, since I'm an advocate of the stock airbox on any lightly modded setups, I've found virtually all to flow better than an open filter.

Good results so far, really interested to see the gains after porting the cyl

[keithw]

I'm also quite interested in seeing what the open airbox plots are like. Currently I have the slide needle at the leanest postion. It runs well except for at the top end where it four strokes. With the 85 I'm likely to need to raise the needle some. My needle is the 5 groove one so I have plenty to work with.

I've got a ported cylinder with a domed piston ready to go on once I get there.

I haven't decided what, if any of the mods I'm doing I would reccomend. I'm just testing and documenting now. The net result so far is that it goes just a little faster and tends to sieze at WOT.

keithw

[keithw]

The head temp gauge arrived and has been installed. It is a used VDO I found on ebay. With the too rich main jet it runs about 300 degrees F. I expect it will be a little higher with the correct jet.

Waiting for the 85 main before I do more speed runs.

keithw

[PimpinSpree]

how do you know the rpms? is there a writeup on tachs on here?

[keithw]

I've got a clip on tach normally used for auto service. You can either clip it over a spark plug wire or the low tension wire going to the coil. I extended the low tension wire going to the coil and velcroed the tach where I can see it. It was a gift so I'm not sure of the price, but I don't expect it was very expensive. I don't see how I could get along without it.

keithw

[keithw]

The 85 main jet arrived. Took it out for some speed runs. Air box cover off, exhaust open, ported intake manifold, 85 main jet.



Is anybody else noticing a trend here? So far no increase in power and a minimal increase in top end. Also, overall it just isn't running as well.

I think I'll go back to the 68 main and put the airbox cover back on. The next two things on the list are a ported cylinder and a tuned pipe exhaust. Any preferance as to the one to do first? The pipe would be quicker to do as all I need to do is bolt it on. The ported cylinder would require some break in time.

keithw