rod growth rate

[Fly1]

Fabian the crowded roller bearing design is old tec, by todays standard.I,m by no way saying your wrong,
for I have read others say the same.I,m just not under standing this.Every racing two stroke I have ever
seen, Kart, motorcycle or what ever uses cage bearings.Now the old chain saw stile engine used the crowded roller bearing design.
But there now history since the mid 1970,s.

Being the Chinese are making these things, I would think it has to have something to do with the alloy.
These engines do not have near the stress load on them as the larger two strokes.If some one has a ole
rod they would send me I would check it & post the results.

Fly

 

[Fabian]

Fabian the crowded roller bearing design is old tec, by todays standard

I agree.
Having needle rollers rub up against each other causes unwanted friction in a high speed application, and as we all know, friction where it's not wanted, results in reduced horsepower.

Every racing two stroke I have ever
seen, Kart, motorcycle or what ever uses cage bearings.

partly for ease of production line assembly, and partly for reduced weight of the bearing assembly and partly for reduced friction - benefits all round.

These engines do not have near the stress load on them as the larger two strokes

I agree. but the standard CDI uses a 4-stroke ignition curve, and when you have an engine that is prone to ignition related detonation, the crowded needle roller bearing assembly has greater load bearing surface area to cope with the hammering effect of detonation.

From my experience (with the Chinese 2-stroke bicycle engine), the crowded needle roller bearing assembly is much more durable in long term operation.
My last crankshaft/connecting rod assembly gave 10,000 kilometers (6,000 miles) of reliable service, though engine revs were kept below 5,000 rpm. Quite respectable life for a $35 replacement item.

 

[Fly1]

Where do you buy the needle from?
Fly

 

[Fly1]

You know I,m still waiting on my bike to come in.But the more I read about these cheap motors,
I think I may just sell the one I have & go the four stroke.If you can't buy a decent rod, crank pin &
so on why invest in a peace of crap, when you can buy a HF motor for $100 bucks?

This just does not make any sense at all.Get stranded some where & push the bike back.I like
playing with two strokes & done it for years.But I never had to balance any two stroke to keep
it running, or worry about the rod, crankpin or upper rod/wrist pin failing.

Nope I think you guy,s have been a great help in solving me a lot of grief

Thanks Fly.

 

[butre]

you don't have to worry about bottom ends unless you're fabian. that guy is cursed or something. The people who are blowing top end bearings are the ones who build a single speed bike and run it at top speed the whole time. My failed wrist pin is a special case because I was using titanium, these things don't ship with titanium anything. I've never heard of the stock steel wrist pin failing.

If you treat these bikes like a normal person would treat them they'll last you a solid 2000+ miles before they need about $30 worth of work.

 

[Fly1]

Titanium (smile).butre I don't know if you read another reply I posted some where about A issue I had
with a titanium rod when I had a kart shop.But I had a customer that bought a bm 130 engine from Appco.
Appco was the importer for bm a Italy based manufacture.Anyway Bobby my friend made maybe four laps
& the engine froze.

We tore it down & the lower bearing was welded to the crank pin.It was a big race at our track & the top
engine guy for bm happed to be there.I took it over to him & ask what he thought.Dan said he had seen
the same happen before, but was not sure as to why.We never use titanium rods again.I don't know
for sure to this day.But after talking to a few guy engine builder I respect, I think it has something to
do with expansion rate of titanium in high heat.

Just guessing but I know it can cause problems with needle bearing engines for sure.

Fly

 

[HeadSmess]

titanium is a fancy, hard to work, common metal. hard to work. it oxidises, it corrodes, it reacts with just about everything, hence why its so hard to come by in a pure form, despite its prevalence in the world around us.

never tried it, my only experience was a...friend... with one of the old sachs velocette engines wheel things. once he broke the (titanium) rim and was quoted a large sum for the new replacement... he got a "rotary" with the steel rim.

i said it before...this forum should be full of people with failing bearings, due to their excessive over revving of 5000+

the fact that it isnt, speaks for itself.

youll find this forum, and most others, are full of mechanically challenged people asking rather basic repetitive questions... the odd real expert...and plenty of self-proclaimed experts.

some threads are quite a good read, while some posts will make anyone that knows better vomit explosively

run it, have fun seeing what you can achieve... on one hand...they can break ya heart by blowing up literally instantly after days of work.

sometimes they just dont want to die and it takes extra perseverance to make em break


this took a LOT of searching to find again!






welding in reed blocks from rgv 50's... opening them up so theres a reason for a 24mm carb

porting...

pipes that actually work (some of them )


like all research, one must sift the chaff from the grain

 

[Fly1]

Ya good reply.You are right on about people & there advise.I never ague any more with
anyone.You never win, but do enjoy discussion.Why people try to proclaim they know
everything amazes me.If you put your self into that prospective, then how can you
ever ask a question.

Oh well I guess I have read to much on these forms & I know better.My bike will be here today
& I checked my engine out, installed a Fred 6cc head & going to break the engine in.Then
check compression once the rings are seated, & pull it back down match ports, adjust squeeze
band on head, for it is way to loose.Then I,m going to build a low end expansion chamber.

No port radical port work.Just some good low end to pull the hills here.

I will post some pic,s of this rig in coming days.
Fly

 

[butre]

the bike I'm waiting on parts for now is an avgas fed twin engine racing bike with case reeds and the biggest carb I can fit in the frame and I still don't expect it to hit 11,000 rpm under load.

 

[HeadSmess]

my nsr150 peaks in at 10,500, and by the time it hits the redline at 11,000 its basically as powerful as at idle... real sudden cutoff!

though once i have a spare cylinder, and whack on a decent exhaust and upgrade to an ignitech ignition unit... that should change to 13000


yup, ignition restricted redline, why bother even printing the tach up to 13.5k if it wont get there?

then i have to get another bike for commuting rather than do it on the buzzbox, which will henceforth only come out on sunny weekends