My first mod.

[DeadPixel]

Decided to try some cheep mods on the old motor before I swap in the built motor. I am still in need of parts for the new motor anyways. My first budget mod is a Brigs&Stratton big block air filter swap. I still need to get a real performance air filter and adapter and thought I would try this tell then. I don't have enough yard to test so cant say if it worked or not yet. Going to take bike to families property were I can ride and tune. The filter fits the top snug so the top stays in place well but I need to figure out how I am going to secure it now as it is snug but not secure. Was going to make a scoop but decided it would probably be too bulky and is best left how it is as it is not in my way. And yes this is getting a real performance filter later guys. Just though this would be fun to try.

 

[SAS289]

Interesting. So you gave it more air. Did you open up the jet at all?

If I were running all stock I would drill 4 1/2" holes in the bottom of the air box and open up the main to about .031 or so. Maybe even poke a few tiny holes in the stock air filter.

 

[DeadPixel]

Have not added more fuel yet. Going to see if I can get a bit at Homedepot tomorrow as I worked yesterday and today. I think it might have caused a flat spot a few RPM after the clutch engages when I hit the throttle. My yard is too small to do good test in. I will see if I can find a .031,.033 and a .035 bit. I plan on making a header for it soon too so will probably have to re step up the jet later. I thought about drilling out the bottom of the box too but decided I would just mod what I have too to make the filter fit.

 

[SAS289]

I'm wondering if you would even experience a noticeable change in power or not. I started out with the open air filter, 140 e tube, and jetted at .033. The rest of the Hisun engine is stock. Runs fine. For the hell of it I dropped down to a .031 and didn't notice any difference. Kinda makes me want to see how it runs with the stock e tube. I should mention that I bought 4 extra jets to play with. And I am running the stock muffler that I ground out the flange area in an attempt to port match it to the gasket. Not great but at least it took care of that part of the restriction.

 

[DeadPixel]

So could not find bits at homedepot but I did get some welding tip cleaners. There pretty much round files. Not sure what size I used but I went one size up on the file. I took the largest one that fit and filed it tell I could fit the next size up and then did a few passes with the large one. I cant find my calipers but either way it runs better and has a little more pep to it. It pulls good and am thinking I will be pretty happy once remove the governor. I do wish it had just a little more bottom end right after the clutch engages so maybe a flat top piston to raise the compression, porting the head and the header will give the extra power I am looking for in this motor. I need to buy some extra gaskets so I can start tearing things apart. Files were $4.50 so I am in the mods for a little under $25 so far. I also see that the return spring is bottoming out. I have the throttle screw all the way out but the throttle is not going all the way open due to the spring being too long.

 

[SAS289]

Yeah chop that return spring to get full throttle. And it's easy enough to add a second spring if necessary. The Coleman doesn't come with the small throttle spring found on clones for years.

 

[DeadPixel]

Just ordered some gaskets and a flat top piston for this motor. Would have loved to do a UT2 flat top and a +.100 rod but cant afford the rod at the moment.

 

[SAS289]

Have you measured "in the hole" on any of the clone engines? I opened up a few of these but do not have the measuring tools. They appear to be at least .030 in the hole. You would think you could use a .020 rod with the stock piston?

I will be using a new old stock greyhound for my second Coleman and am undecided about how far to go with engine before I put it in the bike. I want to stay mainly stock but know that a rod is probably the best upgrade (internally) to do for these engines. The small bump in compression would be an added bonus. I'm such a cheap ass and have a hard time with the idea of putting a $60 rod in an $89 engine.

 

[DeadPixel]

Ok so I got a new battery for my calipers and measured my welding pipe cleaner files. I think I filed the jet to about .033" to .034"