21 3C
 

This is a good engine to start with, not as quick as 35+21 but it is racable and reliable. I was racing this last year before I race the 35+21. Take good care of it and it will be OK.

Regarding the question of when to replace a connecting rod - need to add in all the occasions when you've over revved your engine i.e. two speed mis shifting causing it to go to neutral, when you've had radio issues (recently had a battery pack shift and short out, couldn't hear it from the stand but i'm assuming it revved up because the rod broke next time out) and if you want to be real conservative, when you've run a long main and gotten tires down super small towards the end, compard to the cost of a whole motor a connecting rod is a good investment and easy to change (don't forget the new pin clips either)

I'm pretty good on replacing rods, but what about the wrist pin Rick?

I'm probably a little slack there..... unless I can feel a ridge, or it looks tarnished I let it be. I've only changed a wrist pin once.

A small engine manufacturer i know, for which a friend of my tests engines for, also makes custom conrods for testing in other engines (Nova, Picco, etc.)
They once made a conrod which was so hard, it snapped within 2 tanks of fuel.
A conrod needs to have some flex, so even without visible wear, the possibility exists that it gets tired.

So replacing a conrod on a regular basis is better then only check for visible wear......

A wrist pin will cost about?... 2 bucks?, so I always replace them to.....

you should change it when you change the rod.

thanks, but I was asking Rick.....

Thanx for the reply. I'm still breaking it in but so far it seems it will be the fastest engine I've ran so far.

How long is the lifespan of a ceramic bearing?
And when do you know if you need to replace them?

What is the differance between a PR-21 R01WC and a PR-21 R01WCS??

Depends, but... had some that survived to the practical life of the crankshaft without problems. You will know you need to change them when moving it with the finger it feels gritty.

The key for not ruining a ceramic bearing is to baby it (no high rpms, run them slightly rich) for around 3 or 4 tanks to allow it to fully seat on the bearing races and not spin the balls, if you manage to break-in correctly, the bearing will survive your engine.

i second that my +3CT still has the original ceramic bearings and the engine is a year old they will get replaced soon but if you look after them they last just about for ever and don't forget to run the engine dry when finished for the day and use after run every time

What is the differance between a PR-21 R01WC and a PR-21 R01WCS??

I got a problem with my engine, it is very hard to start and when it finally starts i can run a few laps when it cuts out again and is again very hard to start. We thought it might be the plug so we changed it from an novarossi c6tgc average to a c7tgc cold plug. This didn't help. i also replaced the fuel lines (Which i do before every race) checked if the flywheel was hitting something which wasn't the case. I also checked the clutch and it looked good.

I checked the carb and cleaned it with fuel but there wasn't any wear i could see.

Does anyone have any other suggestions that i can try? As i am quite confused what to do now. :confused:

I have attached a picture of the engine.

ICE:
How much compression/pinch does it have? the piston has quite a few scratches on it. Do you clean/re-oil your air filter regularly? use after run?
how hot do you run it? if the p/s fit is loose, then when it warms up it will stall because of heat expansion.

Is it possible to add metal to the crank pin and then regrind it ? Mine has gone elliptical . Failing that where can I get an 85005 crank for a PT21R01WC ? Thanks .