Reeds and jetting

[deeeebeeeeee]

One of my factory reeds was starting to fray in one spot, so when I found a new set of two stage Boyesen power reeds for $10 I ordered them up.

Installed the new reeds, and resealed the cage and boot with high temp rtv while I was at it.
The reeds came with a "power bar" which is just a brace for the top without the reed stop bit. Instructions for the blaster reccomended to keep the factory reed stop instead of using the power bar.I compromised and used the power bar as a spacer for the reed stop. I don't think it will allow the reeds to open far enough to shorten their life.

Low end runs cleaner, and mid gained as well, it even pulls smoother and harder on top until a point where it seems to unexpectedly quit pulling.
By the sound and feel of it especially in fourth, it's pulling hard and seems like it's wound pretty good but not tight, then it quits when you would expect it to have another 500 rpm.
It's hard to explain, I am sure rpm wise it is pulling to about the same rpm. But before you knew when the power was going to taper off, as it started sounding like it was running out of steam. Now it pulls clean and smooth then whap rpms just stop going up.

Because of this I ask, Do I need to rejet when changing from factory reeds, to dual stage reeds such as the Boyesen Power series?

A little more searching says rejet not usually required, so I guess the question is.
Why is it since changing the reeds that the motor sounds like it could pull further, but instead stops?
Is it that before the reeds running out of airflow at the intake played a role in max. Rpm, but now it does not?
If so what causes it to kinda hit a wall at the top? Is it now running to the limits of the timings, pipe, etc?

 

[Blaaster]

It is not usually required to alter the jetting when fitting Boysen reeds, but who really knows because every engine is slightly different .

Did you leak test after fitting the reeds, it is possible that there could be an air leak around the carb boot/ reed block area?

It is advisable to use the stock curved stoppers as the bars tend to weaken the area where the fulcrum is.

 

[deeeebeeeeee]

It is not usually required to alter the jetting when fitting Boysen reeds, but who really knows because every engine is slightly different .

Did you leak test after fitting the reeds, it is possible that there could be an air leak around the carb boot/ reed block area?

It is advisable to use the stock curved stoppers as the bars tend to weaken the area where the fulcrum is.

Sealed the area up pretty good, this being my first 2 stroke that doesn't cut something, or power a rc heli, I tend to be overly paranoid, ran the tar out of it with me and my 10year old (200 lbs total) in it big up hill section and flat out down the wide road, 100 yards later I am idling across the parking lot, then I get worried when it's a little warmer than usual.
Same thing with the rpm question initially I wondered if it was a problem.I later realized that it was actually winding to the same or better rpm as before.
It became a simple curiosity, since the i take tone was now so clean and sounded like it could easily handle more rpm, what then was the next bottle neck, not as simple as a 4 stroke, can't just open up the exhaust flow and know you will get more power as well as tip your power curve toward higher rpm.
Do the same on the two stroke, and guarenteed your not going to gain anything but a headache.

Got my spare head and cylinder in, they look good for my purposes, looks like someone tried to do some port work behind the reed cage. Thankfully they took very little and not in the window area, like someone was going to work on it, then decided maybe it wasn't such a good idea.

 

[deeeebeeeeee]

For anyone that ends up here in the future, or anyone who may be following . I believe I found what was causing my top end to seem not quite right. It was an exhaust header leak.


Not too long ago when my pipe was off I noticed that my exhaust header was leaking, it was late and starting to get dark so I pulled it off reseated the gasket, put it back on flat and torqued it down. It seemed to be ok. Except the header spring did not fit tight to the pipe and allowed the pipe to rattle.

Last trip out, went slowly through a deep water hole and realized I was blowing bubbles. Turns out the header pipe was defective from the factory. It was welded in at a slight angle and just shy of a mm stuck out on one side.
I cleaned up the header, lapped away the lip of the pipe as wjell as other inconsistencies, and reinstalled with a little copper gasket goo. I also tightened up the spring a little. Warmed the motor a little, and let it sit over night.


Finally got to ride around the house it today not much room to really ride much but I got a hard clay uphill section that gets really slick when it's wet, you literally just have to go up a gear, pin the throttle and try to hit any spots with a little bit of loose dirt on top of the clay. It's really a pretty good test of how hard your motor will tach, and pull at high rpm, especially when you hit spots where there is more traction.
it tached harder and stayed up and pipe on the alot better even when it hit good soft pack dirt and started getting traction

 

[Blaaster]

Thanks for posting your findings I may well help someone.

Leaky header pipes will create a lean mixture because not all of the expelled fuel charge is rammed back into the cylinder by the pressure waves.

2 strokes must be airtight from the air filter to the stinger of the expansion chamber, otherwise problems can occur.

 

[ryn]

Thanks for posting your findings I may well help someone.

Leaky header pipes will create a lean mixture because not all of the expelled fuel charge is rammed back into the cylinder by the pressure waves.

2 strokes must be airtight from the air filter to the stinger of the expansion chamber, otherwise problems can occur.

How might one leak test exhaust other than taking it through water and look for bubbles and intake components? I am leak testing engine now and fixing those leaks. The exhaust/intake components are my next task.

 

[Blaaster]

Exhaust leaks will ooze oil.

 

[ryn]

Alrighty well that is easy enough to look for lol