Sounds cool about making the hole bigger, which im really curious to see how long it will last you. Could be possible about the reason that you have listed that could cause the Crank pin to break, but why does it also break when the engine is brand new from the box and running on the first tank on the track with rich settings after coming of the bench after 3 Tanks of idle? i would rethink about drilling that hole bigger. But good luck anyway and keep us posted, like i said im intrested and i hope it works. Just might be another improvement that could done.
Cheers

well i do have a few opinions about this engine already. and maybe it was read wrong about the hole. im talking about the inner part of the crank, elongate the hole in the direction the fuel is coming in from. so this would effectively double the area to catch the fuel on the way through, but in no means to drill the hole bigger, that will weaken the pin.
this is by far the tightest engine i have ever run in. normally preheating and engine to 70-80 c works a treat. im having to get 100 + to prevent the piston from getting stuck on tdc. that is a huge stress on the rod and the pin. all care taken runnign in the engine, and keeping heat into it while it runs , all helps on the rod and pin issue. but i guess ill be seeing the results in a few weeks. adding the extra shim while running in will also help, and running it in with a higher oil content and 16% fuel will also help. i wouldnt be hitting the track with it in the first 2 tanks, its too tight, i have 4 tanks through it now , just my opinions thats all.

I have the VZ-R engine modified by Uriah M, and he has elongated the rear portion of the crank just like you are saying. The Next time I have the engine apart I will take a picture of it and show you. I wraped a towel around the cooling head to keep the engine temp up, but yes it is still very tight with the added shim and approx 1/2 gallon of fuel through it. I use a heat gun to warm up the engine everytime and to reduce stress on the Rod.

good to know im on the right track then. let me know how the murnan mods go. i see so much potential from this engine if it goes good std.
i think its a great idea to channel the fuel from inside the crank, its a fresh burst of fuel and oil straight from the carb, no matter where the piston position is. but a failsafe option is to run a rod with the oil hole as well.

Im with you now, sounds like a good a idea, and yes Patto, OS motors are very tight and you do have to get alot of heat onto the crank and head to get it to idle on the bench without locking up,which is why i like to use Foil to wrap around the head while idling and keeping it nice and warm from the first tank.im Glad you mention the part about the Rod and Pin going under alot of stress from the first start up and everytime it locks,that cause heavy stress to a rod. But some ppl just dont want to believe you.would love to see it run after any modds you do to it. maybe you could YouTube it?
Good Luck with it
Cheers

its hard enough to find a pitman on raceday, never mind a camera man
ill see how it goes first before any mods.

i ran the motor yesterday and i can say it has a broad power band. smooth from low to high. was running rich still, but easily beat my fastest lap time while running rich. i am impressed, it is stock as a rock, and i feel there isnt much need to mod it much at all. the only thing maybe is for the factory to look at how tight the damn thing is, i mean does it really need to be so damn tight ? anyway, it ran flawless most of the day, well till i broke me car
i will look at getting another one soon as a back up for the states.

Did you completed the final ?

From my personal experience, this engine is not suitable for circuit with long straight ( not okay for flowing high speed circuit ). The engine become sucks after 23 minutes..... It become lame and sometimes die ( DNF ).

Becareful with rear bearings.... if it feels gritty, quickly replace it. A while ago before I know this, I keep using it and the engine eats lots of glow plugs.

If anyone is interested, I have for sale a O.S. 2040 pipe and header. Perfect fit for this engine.

O.S. 2040 Pipe & Header

Thanks for looking...

I stocked up on plugs when I had my VZR. It was a great engine for the money. If anyone is interested I have 3 P7 and 5 P8 BNIP glow plugs available. They cost me $9 each 2 yrs ago., I just found these, and have since moved to another engine.

I'd like $50 shipped anywhere in the lower 48. paypal preferred. pm me your email address for pics.

Thanks... J

hi im new to nitro just got a o.s.21v-spec and wood like some help
on how to use the shims that come with the motor i read the manual
and it was not to informitive like to hear from some one
with frist hand experiece had posted this in nitro off road not much
avice on shiming the head thanks