Question about Long-rod engine….

[burnin'_oil_2001]

I have read about the benefits of long-rod engines for years and was wondering about doing it to one of my blasters. I know that they are available for banshees but I have yet to find one for the blaster. Has anyone on here had experience with a long-rod blaster? I was thinking that it would be most beneficial to do a long-rod big bore 240 kit to help improve the reliability (and add displacement and hp) of the 240 kit. Because of my size I rev the piss out of my blaster when I ride the dunes and desert and would like to have a big bore that I can ride in the mountains and let friends/family use in the dunes w/o worrying about reliability. :-/

 

[X-Runner]

What is a "long-rod?" Stroker crank?

 

[burnin'_oil_2001]

What is a "long-rod?" Stroker crank?

Basically, it is a longer rod and it is supposed to relieve piston side load pressure by lessening the rod angle. I have been told that this is the preferred method for getting a longer stroke as it is not as hard on the engine. This may not be an issue with a stock bore blaster due to its short stroke, but I think it would be better for a big-bore kit. I found a quick link to a website with banshee kits available.

Banshee Prodcuts

 

[BLASTER HP]

when a banshee has a long rod it uses blaster pistons becuz of the diff pin height, if you put a longer rod on a blaster you'd have to find a piston with a higher pin height to compensate for the longer rod or your piston will smack ur head sumthin fierce to my knowledge there isnt another piston out there that has those specs.

 

[super noober]

when a banshee has a long rod it uses blaster pistons becuz of the diff pin height, if you put a longer rod on a blaster you'd have to find a piston with a higher pin height to compensate for the longer rod or your piston will smack ur head sumthin fierce to my knowledge there isnt another piston out there that has those specs.

no offence or anything but i doubt a 350cc dual piston banshee uses 200cc pistons at any time. if im wrong my bad.

 

[YZ Otis]

Long rod just decreases the rod angle. Less stress and more efficent transfer of power from piston to crank. Doesn't change stroke. You'd need a spacer under the jug if you could find a compatable rod. Not worth the effort for an everyday motor. IMHO

Shee's that use Blaster pistons arn't 350's anymore. Don't race'm with a Blaster

 

[blasterfreek30]

a stock banshee piston is 64mm, stock blasters are 66mm

 

[super noober]

a stock banshee piston is 64mm, stock blasters are 66mm

thats actually closer than i thought it would be. so if you bored a banshee out 2 mill then you're there? my bad blaster hp :-[

 

[diesel]

In my experience from the TRX250R side of things, the difference in rod angle isn't really that significant, short-rod versus long-rod. I know this is a Blaster site, but the Honda 250R is such a perfect example of connecting rod differences...

The 1985-86 ATC250R and 1986 TRX250R have a 125mm connecting rod.

The 1987-89 TRX250R have a 130mm connecting rod.

These machines all have a crankshaft with a 72mm stroke.

When the crankpin (where the connecting rod is attached to the crank) is at the 3 o'clock and 9 o'clock position, rod angle is the steepest. Using trigonometry you will find that the 1985-86 short-rod 250R engine has a rod angle of 73.26 degrees (measured from horizontal). The 1987-89 long-rod 250R engine has a rod angle of 73.92 degrees (measured from horizontal). That's only 0.66 degrees difference. It is also worth mentioning that the 1984-2001 Honda CR250 dirt bike uses the same 125mm connecting rod as the 1985-86 short-rod 250R. So I don't think you need to worry about having a stock Blaster connecting rod.

 

[Paulie B]

no offence or anything but i doubt a 350cc dual piston banshee uses 200cc pistons at any time. if im wrong my bad.

Yes they do on certain big bores.
No offence taken!
Shees go all the way up to 521cc with the stock stroke.

 

[Paulie B]

I have a 'long-rod motor'
83mm bore
75mm stoke
but I use a YZ490 rod.

 

[BLASTER HP]

paulie, you have a 19mill? stroker with a 83 bore, what cylinder do you use ?

 

[Paulie B]

paulie, you have a 19mill? stroker with a 83 bore, what cylinder do you use ?

I have a YZ400 2 stoke.
Sorry for the confusion!

 

[hickskateboarder]

lol

i wanna ride that thing. my blaster (stock bore minus one rebuild) keeps up with my buddies big bore z400. i can't imagine that thing...

 

[Paulie B]

I'll have some new vidz up after I get back from Busco I:I

 

[FLOTEK]

Long rod just decreases the rod angle. Less stress and more efficent transfer of power from piston to crank. Doesn't change stroke. You'd need a spacer under the jug if you could find a compatable rod. Not worth the effort for an everyday motor. IMHO
QUOTE]

agreed .............a longer rod wont make anymore power ,there will be slightly more dwell time and less angle for potential cylinder wear improvment but the extra mass thats thrown around will negate any power benefits and that mass can reduce the peak rpms of the little mill ....110mm stock is plenty long for that given stroke

 

[Kennedy_Power]

The longer rod does not add displacement
Displacement=
BoreXboreXstrokeX3.1416/4
Blaster set up
66m bore and 57mm stroke
Move the decimal place by one to change from mm to cm
(6.6)(6.6)(5,7)(3.1416)/4=195cc
The long rod will have less rod angle and less thrust against the cylinder bore

 

[burnin'_oil_2001]

The longer rod does not add displacement
Displacement=
BoreXboreXstrokeX3.1416/4
Blaster set up
66m bore and 57mm stroke
Move the decimal place by one to change from mm to cm
(6.6)(6.6)(5,7)(3.1416)/4=195cc
The long rod will have less rod angle and less thrust against the cylinder bore

Ok, I understand the rod length will not change the displacement (actually once I started to think about it and do the math it became clear) but push the piston slightly farther up into the cylinder and use the same stroke provided by the crank. Would this not be beneficial to port timing (due to port blockage a bdc) and would a long rod be better for a higher reving engine- or one that spends much of its time wide open? This may not be the case for the Blaster, but I have heard from local builders that with the short stroke of the Blaster that there is more side load on the piston and cylinder walls and can cause problems for people who ride in the upper 1/3 of the rpm scale when using big-bore kits. However, I have been bitten by the sand bug and am thinking about having my second Blaster's engine built for the dunes- the last couple of times I was at the dunes I spent most of the time chasing people on banshees' and 450rs'. I figure that most of my time is spent at over 7k rpm wound out in third and depending on the grade 4th gear. I know that I am going to have to gear down (probably 20%) to get more use out of 5th and 6th. Top-end speed is less important as being able to maintain wheel speed for climbing the dunes, side hilling, and tree shots. Currently, I ride the dunes between 50-100hrs a year and another 50hrs a year elsewhere and I am looking for a reliable mid-high power package for the dunes. This is why I was considering the long-rod teamed with a big-bore kit. So, since I rev the hell out of my motor (to keep up w/ others) does it make sense to stick with the build you suggested for my main Blaster and not plan on upgrading it to a big-bore down the road. And to build my second Blaster for dunes only with a big-bore stroker (or other build)? I also try to use the responses as a learning experience and appreciate how friendly and patient that you and the rest of the builders on the site have been- thanks for your time.

 

[burnin'_oil_2001]

Long rod just decreases the rod angle. Less stress and more efficent transfer of power from piston to crank. Doesn't change stroke. You'd need a spacer under the jug if you could find a compatable rod. Not worth the effort for an everyday motor. IMHO
QUOTE]

agreed .............a longer rod wont make anymore power ,there will be slightly more dwell time and less angle for potential cylinder wear improvment but the extra mass thats thrown around will negate any power benefits and that mass can reduce the peak rpms of the little mill ....110mm stock is plenty long for that given stroke

Thanks, I am learning and trying to filter the chaff from the truth as I have heard so many opinions over the years. I have people telling me to go with a 240 kit and others saying 265. I definitely want the best bang for my $$$. I have ridden 4mil big bore Banshees (80-90hp on premium) and they are great but they are also hard to manhandle due to size and this is why I love my Blasters. I would run race fuel to get a reliable dune able Blaster with mid 40s horsepower. I have found that I like more technical riding than flat-out on the flats- though I do have to do this to follow the other quads.