Factory Pipe: ltd vs mod

WAB

WAB

salty nuts
Location
coastal GA
Anybody ever switched out just the chambers to see the difference?

Which is supposed to be better for low end?
 
Frosty

Frosty

New York Crew
Location
Western New York
limited is supposed to make more low end power I believe... mod more mid range. I have a mod, and would love to buy or trade for a limited to see if there is any noticeable difference.
 
Sanford

Sanford

ECF
Location
Freeride capital of the world
WAB said:
Which is supposed to be better for low end?
Click to expand...
The limited is better for low end (by design and function). The difference will depend on overall motor setup...and possibly at the expense elsewhere.

The effect of having a shorter chamber (mod) is to raise the power curve a little higher to better suit the 62T/61X ('96-up) combo. The limited chamber was the first chamber for the 701 back when only the 61X/61X was around. The mod chamber was the result of racers/racing looking for more out of their early race setups (this is also how it became known as the "mod").
 
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WAB

WAB

salty nuts
Location
coastal GA
Ok, maybe I need to play with the water injection screws some more.
My friend has the ltd (shorter) and his ski makes power quicker than mine off bottom end. I have the mod chamber (longer). He has a 61x cyl and I have a 62t, both at 81mm, and the exhaust ports are pretty much at the same height, same props, & same basic mods on both. :shrug:

he must have one of those aftermarket powerbands or something. :rolleyes:
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
WAB, if you have a 62T cyl, and he's got a 61x cyl, the exhaust ports are not at "pretty much the same height".

The 61x would develop the power sooner than yours, I would think.
 
WAB

WAB

salty nuts
Location
coastal GA
Matt_E said:
WAB, if you have a 62T cyl, and he's got a 61x cyl, the exhaust ports are not at "pretty much the same height".

The 61x would develop the power sooner than yours, I would think.
Click to expand...

Yeah, I know about the exhaust port differences in the 2 cylinders.
But these are both ported to about the same height. I don't care what anybody says, his makes killer low end power with the raised ports. There may be other differences in the 2 cylinders like transfer ports/roof angles and other differences I don't know of.
 
Idok

Idok

F1pro
Location
Nations oldest muthaF+++kin city
the differnce between the 2 boats andy's talking about is freaking HUGE>..


scott's hits like a sledge right off idle....

andy's hits like a....................................well, anyone ever see shawsank? "its a rock hammer" (sorry buddy :wall: )..but def has good midrange...




andy, did you ever figure out the timing advance? is your stator set to stock or advanced???????


sounds like it may be time for a new cyl.....
 
WAB

WAB

salty nuts
Location
coastal GA
It's too wet, I know; thought it would be safer that way. I've been running it with the bottom screw open at least a half turn, middle closed, and top one open about 2 turns I think.
I have the stator set advanced (counterclockwise) 2-3mm. Stock head.
 
douglee25

douglee25

m3booooy
Location
South Jersey
WAB said:
It's too wet, I know; thought it would be safer that way. I've been running it with the bottom screw open at least a half turn, middle closed, and top one open about 2 turns I think.
I have the stator set advanced (counterclockwise) 2-3mm. Stock head.
Click to expand...

Yes, I would agree it's too wet. Close your top screw and bump your compression to 175psi or so (watch your advance). It should run much better there.

Edit: I didn't mean close the top all the way (1/2 - 5/8 open).

Doug
 
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Y

yamaslut

Guest
Andy... shut the bottom screw and open the top till 7 threads are showing....
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
Those are small threads. Do you hang over the headpipe with a monocle, Nick? :biggrin:
 
Frosty

Frosty

New York Crew
Location
Western New York
yamasaki said:
3mm advanced is what i ran my last 760 motor at. fook it, take it to 4-5mm... :biggrin:
Click to expand...

Not too threadjack here, but... how much timing advance can you safely go with this setup or should I not even bother? And what implications for reliability and longevity are there with doing so?

2001 Superjet -
OEM 701 cylinder - Magoo freeride ported
Factory "B" mod pipe
ADA head w/35cc domes ~175-180 psi
stock flywheel (for now)
stock ignition
Pro-Tec modified CDI - adjustable rev limiter
stock 38's (for now - going to put on a set of 44's this fall)
dual cooling
13/17 solas with 3mm cutback
bore reduction nozzle

thanks for the info...
 
douglee25

douglee25

m3booooy
Location
South Jersey
TXJFrosty said:
Not too threadjack here, but... how much timing advance can you safely go with this setup or should I not even bother? And what implications for reliability and longevity are there with doing so?

2001 Superjet -
OEM 701 cylinder - Magoo freeride ported
Factory "B" mod pipe
ADA head w/35cc domes ~175-180 psi
stock flywheel (for now)
stock ignition
Pro-Tec modified CDI - adjustable rev limiter
stock 38's (for now - going to put on a set of 44's this fall)
dual cooling
13/17 solas with 3mm cutback
bore reduction nozzle

thanks for the info...
Click to expand...

It's hard to say because every setup will vary slightly for multiple reasons. It can even come down to the weight of the rider. I would say with all the items you have listed, 3 degrees advanced would be a good starting point. Make sure you run the best gas you can though. Def. keep an eye on things though when you start playing with advance. Things tend to destruct very quickly.

Doug
 
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