Two-stroke performance tuning?

[F5 Dave]

Glad to see we are back sparring as normal, thought everyone had gone soft.

erm my pre 95 RS didn't vibrate that bad at all actually, yes the 97 I rode was probably smoother but not something I thought about (as opposed to man this thing is so much more roomy). They can vibrate a bit when jetting is off or perhaps the front mounts were broken or the crank turned on the web. That will make anything vibrate like a jackhammer.

[quallman1234]

Without having any thing to back it up, my experience is yes, a perfectly balanced engine does spin up better.

Have you ridden a pre 1995 Honda Rs125R?

My god, (no balance shaft (full circle crank), they where physically exhausting just riding 10 laps.

By comparison the 1995 and later (balance shaft) where like a Toyota Corolla (comparitively that is) Yet, the crank weighed the same (well near enough I guess)

No haven't ridden a pre 95 one.
The one i use is a 98 i believe, and is very very smooth with very little vibration.

The TF125 is quite viby (no balance shaft), hopefully adding another engine mount will stablise this enough too ride.

[F5 Dave]

If you run the TF at reasonable revs it will vibe like a beast, I'd read Spodpro's post carefully with what he did to his, I won't offer any real advice as I've never had to tackle this issue so never researched it with more than a cursory glance.

[Pudding]

A quick search on the net for "Motorcycle Crank Balance Factor" and I found a lot of talk about factors ranging from 55% to 85% and in general the factors were 60-65%. There was one place that talked about 50% with a balance shaft but I saw no low numbers like 25% that SS90 talks about.

[Skunk]

Glad to see we are back sparring as normal, thought everyone had gone soft.

Yeah, without the sniping it would just be informative rather than entertaining as well.
I'm planning a 400 twin at 90° firing so this balance stuff is of interest to me.
Thanks for the info so far.

[saxet]

Think I'll go and watch something with a better I.Q. level involved..maybe Jerry Springer. I'd rather listen to banjo's than this.

[FastFred]

Yes, its a bit more intelligent over on the ESE Works Engine Tuner thread.

[speedpro]

I made a jig that allowed the crank to rotate freely on bearings. Then I laid the rod out horizontal with the piston, pin, rings, and clips and weighed everything on the end of the rod, including the end of the rod. Being horizontal the measured weight of the rod end effectively was the reciprocating part.
Next I made a small double ended arm with a free pointer rod at each end. The two rods balanced each other. Each rod was attached to the arm at exactly .5 the stroke and therefore were centred on the bigend pin. I attached the arm to the crank with one rod mount centred on the bigend and hanging down. The crank main pin and big end pin were horizontal. Because the crank was free to rotate the other little rod was free to press down on a pair of scales. I measured the weight being applied to the scales by the rod. When this measurement was made the rod was still horizontal and therefore the rotating end of the rod contributed to the measured weight, actually it reduced the measured weight. The % was simply the weight measured at the little rod divided by the piston weight etc.

[Skunk]

I've read that several times and still can't picture it. Got a diagram?

[k14]

I've read that several times and still can't picture it. Got a diagram?

Glad you're not the only one!!!

[speedpro]

I'll get the crayons out

[Skunk]

Ya taking long enough... is ya zimmer frame broke?

[Kickaha]

Ya taking long enough... is ya zimmer frame broke?

Thats abuse, you causing trouble again?

[speedpro]

Had other things to do.

[Buckets4Me]

I now see why your engine fell apart in such a short time

nothing is straight or round it's all over the place

on a more sober note you planning to get to Taupo this year ?????

and or Mt Welly this weekend ??