Originally Posted by
leapinglizard
i couldnt keep a tune and had tryed everything so i took the motor apart and saw that the rod had wear at the top and bottom hope its not happening to everyone get ahold of massive mods.
I wouldn't worry too much. I know from what I have read here that Giz looks after his motors very well, and like he said - it was due for replacement anyway.
These nitro motors are very high performance engines, and as such require the care and attention, and maintainence (regular & preventitive) of any high performance race engine. Because they are so tight when new it is paramount that the rod and wrist pin is changed at the two gal mark after break in. I change the bearings, rod, wrist pin and C clips every three gallons on both my race motors (not an expensive exercise with the price of GO parts), and have never had a problem. Plus I can then go racing with the confidence that my motors will perform flawlessly when I need them too.
A lot of guys just break their motors in, then expect them to run for 10 gal or more without even taking the backplate off and having a look for rusty bearings or anything. With a motor this size putting out close on 3 hp, it just doesn't work that way. If not maintained carefully, something will fail sooner or later for sure.
If the rod is getting sloppy, replace it straight away. Check for bearing slop or wear at the same time. I think the best policy is - if you change the rod because it's worn, then you should change wrist pin, clips and both bearings as well at the same time. Might sound like overkill, but better safe than sorry.
Originally Posted by
Fletcher6371
HYPOTHETICALLY
How much run time should a 7-port (Standard Plug)(A3 or 8)with a Dynamite 053 pipe, 6.0mm, Byrons 30% 11%oil
I'm probably way off on my tune because I'm getting temps at like 265+ with only 7-8min runtime once it warms up (cold it only gets like 5min). It bogs coming out of the corners just a bit, nothing too bad, and just awesome mid to top end. I just can't figure it out.
Sounds like you are too rich on the bottom (possibly with a wide idle gap) and too lean on the top. With your set up you should be getting around the 9 - 10 min mark I would have thought.
Set the idle gap to .7 - 1mm (use the pinch test method described by MMods on Page 431, 4th post down) then tune for LSN fisrt, then HSN, then revisit the LSN again to make sure it hasn't changed. The needles on these carbs are very sensitive so only adjust 1 hour at a time until you get it right.