RT carb, with ARROW REED

[JonnyR]

reeds work when you modify the cylinder to increase the timing the port is open usualy from opening the port and clipping the piston skirt

 

[bigbutterbean]

Reeds are not going to add performance by themselves. Modification is necessary. If you bolted the reeds on and didnt do ANYTHING (didn't drill the piston OR port the cylinder), then of course you wouldn't notice a difference. If you drilled the piston and did NOT port the cylinder at the same time, you might notice a difference you might not. If you ported the cylinder AND drilled the piston at the same time, you should see an increase in top end, but probably not bottom end. Since you drilled so many holes in your piston, there are 3 possibilities. One is that you did not port the cylinder correctly. Another is that you drilled TOO MANY holes in your piston. A third possibility is that the first two are both true (drilled too many holes AND did not port the cylinder correctly). When drilling a hole in the piston for reeds, you only need one hole in the correct spot. But the real advantage of reed valves is case induction (porting the cylinder). Where and how you cut the ports on the cylinder determines how it will affect your powerband (the powerband is the range of rpms through which the engine runs most efficiently). Typically, piston-ported (non-reed valved) 2 strokes have a very narrow powerband. When porting the cylinder for reeds, you can port for performance boosting at a specific rpm range, which requires port mapping, or you can port for a gain across the board. I recommend porting for a gain across the board. That thread where I linked to a picture of another member who had ported his cylinder for reeds, did you read the thread or just look at the picture in post #39? If you read that whole page, you may gain a better understanding of reeds and cylinder porting.

 

[Geebt66cc]

Yes, I'll look at it more closely. I was told that I shouldn't cut the half circle on piston skirt when using a reed valve. Also, I was told that it really doesn't matter how many holes I drill as long as there in intake window?

 

[Geebt66cc]

Thanks again..............

Yes, I studied that before I cut anything at all. I was just thought that maybe that was a bit too much. Guess not huh. Uno, BBB I could take jug off again soon, and do just what he has done to jug?! Do you think that if I did that that I still could get away with keeping this holy piston? Like I said, as far as the drilling, I did it pretty well. See, just hate that I drilled 7 holes, but like I said, I was told I could drill up to 9............Really? Anyway, at this point, I really don't see that it could hurt. I just don't want to affect the compression, because I'm still sitting right at 130pounds. Like I've said, can't really tell that I did much anything? Motor on bike still is very clean outside and in, and now still at 700 miles runs out well. One thing that he kept on saying was with using the Arrow reed vs the RS reed, that the Arrow even needs more crank case pressure due to reeds being farther back from motor.? Like I said, it start well, and smoother now................just not any big change at all.

Listen, I also wanted to tell you the only other thing I did was ramped the very top at the intake.

 

[JonnyR]

if you want to do some mods to the piston read on here about piston skirt clipping and piston ramping you might have made holes to high up and arnt getting 100% out of it

this is what i still say on the subject

 

[Geebt66cc]

Hey Jonny,

So, uno, I didn't clut piston skirt at all............. I was just told not to do that using any reeds? .......but maybe that would help? Uno, marked at TDC threw intake.........

 

[Venice Motor Bikes]

There's a reason that the three Arrow Motorized bikes always finlish 1st, 2nd & 3rd at all of the motorized bicycle races... Dave Rust knows his sh*t!!

The Arrow reeds are a proven race winning product; but you can't simply just bolt it on & go... You have to understand that the engine will need to have massive internal modifications, a quality expansion chamber, & a properly jetted carb to achive the full power potential that his reed valves will produce!

 

[Geebt66cc]

Venice, Yeah, I studdied this whole site on everything that you were doing. TRUE, I very much agree when it comes to getting them to work. So,do you also think I should go ahead , pull jug again, and trim piston skirt as well? (It's a 2010 Grubee Sky 66cc)

Ps-I mean do I mark then trim piston skirt either way? I just really like pull power more than tops!!!!!!!~

 

[Venice Motor Bikes]

All of the engine mods I've done make more top end, & not bottom end power.
To try to keep a good 'high-low' balance on my race bike I use a 38t rear sprocket. (Keep in mind that I'm 210 lbs). :/

For more bottom end power you should keep the header pipe long & use a larger rear sprocket.

 

[Geebt66cc]

True, True, I've got coming also a RT carb. From what I understand, that will help some, with a better home base to work with. Venice, I'm also living in SW Va..............HILLS!~That's why I keep a 44t, not to mention I'm sitting at 255....(Just me, not including bike)........

I've always had good luck with Jaguars ideas...........so that's why I drilled 7/32 holes in piston on intake side.