Long Rod...

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Syndicate Performance Designs are the ones that make the long rods and long rod cranks. They are the ones that the engine builders get them from. They make them in 2, 3, 4 and 5mm longer. OBR has tested different lengths and said they have not seen any benefit in going over 3mm and is all they use. When using a long rod you have to put a spacer between the case and bottom of the cylinder. You all so have to use a coil drop to get the ignition coil down low enough.
 
my new motor is a 2mm long rod with a 29cc head and stuffed crank weights it takes the cc up to 30.5 by using a 1mm copper gasket. i,ve only run it for half a tank but it runs well and has got mega grunt low down.
 
pablo said:
my new motor is a 2mm long rod with a 29cc head and stuffed crank weights it takes the cc up to 30.5 by using a 1mm copper gasket. i,ve only run it for half a tank but it runs well and has got mega grunt low down.
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Sounds good Pab. Get some vids posted :cool2:
 
pablo said:
my new motor is a 2mm long rod with a 29cc head and stuffed crank weights it takes the cc up to 30.5 by using a 1mm copper gasket. i,ve only run it for half a tank but it runs well and has got mega grunt low down.
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Sounds like to me you have a stroker crank and not a long rod crank. Big difference between a stroker and long rod. You can get a stroker crank with a long rod but the longer rod does not change the stroke.

Sounds like you have a 36mm bore with a plus 2, 30mm stroker crank which gives you 30.5cc. When you run a long rod you have to have a spacer between the cylinder and case and the cylinder has to be ported for it.

longrod2_1_2_1.gif
 
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All so if you are running a cylinder that is not machined for the stroke and only running a 1mm gasket hope you checked the squish. When running a thicker gasket with a none machined cylinder it changes the port timing. This is why most engine builders machine the cylinder for the stroke then stacking or thicker gaskets.

One of my 7 engines I have built is a race ported 30.5 with machined cylinder.
 
You are going to have less torque with a long rod and more mid to high range power,so that would mean less low end grunt,so you probally do have just a 30.5 modded motor,which you would get more low end grunt from this setup.
 
From the dyno sheets I have seen the long rod gives all around better performance all thought the RPM range including low end torque if using a good pipe matched for the motor. Being you have less friction.

longrod1_1_2_1.gif
 
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Honestly dyno sheets in my opion don't mean jack,the preformance gain your going to notice is what counts,and trust me,if your running a heavyier 4wheel drive your better off going with a 30.5,i have a Long Rod motor,and have 4 30.5 fullmodds and in my4wheel drives i would take the 30.5, your not going to see that 7.5 horse that Oneil bros puts out,until your in much higher rpms,and with 4wd you need more of that power kicking in at a much lower power band.
 
I agree a dyno is a good tuning tool and not real time. But they do show comparisons be between set ups done on the same dyno with the same conditions. I have been working on Harley s for 40 years and know the benefits of a long rod. A lot has to do with having a good pipe matched for the motor and being well tuned. ;)
 
46u said:
whittron who built your long rod motor or did you build it?
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I have a guy out here in MI,build my motors,he also builds some of the fastest boat motors,he mainly just does local stuff some out of state,but has another job building test parts for either Chrysler or GM,so dosent devote all his time to building these motors,but i have ran my motors agianst oniel bros motors,and after seeing the diffrence i wouldnt have anyone else build me a motor,i do no my stuff about motors,i was rebuilding motors when i was 15,but when it comes to porting on the 2 strokes i would rather have someone who has a lot of expierence,and lathe and the other proper tools for releiving pistons,and top of cylinders,to get maximum preformance out of them.
 
And buy the way you are right,having a tuned pipe thats right for your motor does make a big diffrence,but also running a longrod motor in a 4 stroke valve motor then in a 2stroke piston port motor,there is a diffrence.
 
What I was saying about dynos if you have two motors similar one with long rod and one with stock rod and you dyno them on the same dyno in the same environment and one shows more torque then the other this is a good indication that one has more torque. The dynos that most run put a load on the motor or at least the ones I am talking about.

I do agree the numbers many come up with on these small engines are not accurate. I know some calibrate their dyno by using a stock Zen engine. What they calibrate their dyno at is higher then what the Zen websites states so this is going to make the numbers higher. I am all so believe Zen does not dyno their engines but comes up with the rating by the numbers not a machine. I do not think there is really a standard for measuring these engines but if you use the same dyno in the same environment will give you a good idea of changes made and difference between motors.

I have been a motorcycle mechanic and machinist for 40 years and even have a small engine machine shop in my basement. I go as far as rebuild rods, balance flywheels and assemble and true cranks as well as MUCH more. I worked on my first motor in the mid 60s. I assure you the same physics of a long rod in a 2 cycle or 4 cycle is the same. When porting a long rod it is different then a stock rod and if not done correctly will not get full performance. My guess it has more to do with port timing.

I am not trying to have an argument but a conversation and all are entitled to there own opinion. All is good and thanks for the input.
 
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