Break in suggestions

[JohnT_98300EX]

Just got the EX back. +.080 Weisco @ 11 to 1 compression, stage 1 HotCam, CT Racing head (5 angle valve job, port / polish). Running a 40 pilot jet and a 132 main. This is up from a 38 and a 128 prior to the rebuild.
The cam break in is done, no more. I have a LOT of money wrapped up in this. By my wallet at least. How would you proceed from here if it was your ride?

[TRX-330]

When i re-build my engines i have a small electric motor i hook up to the flywheel by a belt, i made a pully to thread in where the bolt hold the flywheel. I let it run for 5 min, give it about half hour then 5 min, half hour, 10 min, half hour, 10 min, half hour. Then i let it run for and hour sit for and hour then another hour then sit for a couple hours, then i usually let it run all night for a complete break in. I will still take it easy on the bike for about two weeks then i will start to rip on it. Now you dont have to do this my way. Instead of the electric engine you can just start your 300 and let it run those times i stated, but just leave out the running all night and just put around your back yard in first gear till you feel you are able to go ride easy.

[JohnT_98300EX]

Thanks for verifying just about what I was thinking. Not going to hook up an electric motor, *LOL* just will start and run it, let it cool, run it let it cool and take it easy.
Thanks

[TRX-330]

Yep thats what i used to do, I came across this electric motor for free and its cheaper to run that then pay for the gas to break in an engine.

[JohnT_98300EX]

First 2 break in rides are done. 10 minutes each, no more than 1/3 throttle, vary the rpm.
Runs fine at and just off idle, stutters a bit from that point to say 1/3 throttle, then clears up. I may be a bit rich on the needle setting? Down low is good, then the stumble (gut tells me it's rich in the middle) and then it starts to RIP once clear of the stumble point. If I put a fresh plug in the warm engine and then run for a while at the stumble point will reading the plug tell me what I need to know?

[JohnT_98300EX]

I had more than one person tell me that +.080 was to big for the 300EX. There is a LOT of sleeve left at .080 over so maybe break in procedure is what their problem was.

I found this on the CT Racing page. Props to CT for posting it.
Break In Procedures
1) Start your engine and let idle occasionally blipping the throttle for four to five minutes. Allow the engine to cool completely. Repeat this "heat cycle" process four more times.
2) Warm up the engine again and ride the bike for five to seven minutes at a very easy pace, vary the rpm, don’t ride at one speed. Don’t ride at more than 1/3 throttle or more than 1/3 rpm. Let the engine cool down completely and repeat the initial break in ride. Let the engine cool down.
3) Check the base nuts and head nuts for proper torque, check the coolant level and add coolant as necessary.
4) Ride the bike for five to ten minutes at a moderate pace, vary the rpm, don’t ride at more than 3/4 throttle or more than 3/4 rpm. Let the engine cool completely and repeat this secondary break in twice more.
5) Replace the spark plug with a new one. Ride the bike for five to eight minutes at a moderate pace, vary the rpm and shift up and down the gears. Once the engine is up to operating temperature you can make a jetting pass. Start in second gear and ride at full throttle through fourth gear, fully revving out fourth gear. With the throttle wide open in fourth hold the kill button down, pull in the clutch and stop. This is called a "plug chop"
6) Read the spark plug. With a pocket flashlight and a magnifying glass look at the porcelain part of the plug only, as you view the plug from the center electrode look down the length of the porcelain to its base, at this point there should be a dark chocolate colored smoke ring. There was not sufficient time to thoroughly color the whole plug, so the nose of the insulator may still be white, as long as there is a visible dark ring at the base everything is OK. Remember we want break in jetting so the plug should read rich/dark. Richen the jetting as necessary. If your having a hard time reading the spark plug, after the jet pass put the plug in a vice and hacksaw around the plug at the washer. Break the threads off with vise-grips, and the porcelain will be easy to read.
7) Complete the break in by riding at an aggressive pace for fifteen minutes, vary the rpm and don’t cruise at part throttle, ride hard without revving the engine too high. At the end of this final break in session do another jetting pass/plug chop as described above. Check the spark plug for the correct dark/rich condition. Wiseco Piston equipped engines will require another one or two break in cycles, ride at a recreational pace not revving the engine hard, full throttle should only be used for very short periods, fifth and sixth gear should only be used to cruise, ride one tank of gas through the engine in this manner to complete the break in. We feel it take about two gallons of gas to break in a motor equipped with a cast piston and five gallons for a motor equipped with a Wiseco.
8) Replace the spark plug with a new one, ride the bike aggressively for eight minutes and do a jetting pass/ plug chop in fifth gear. If the porcelain color is still dark/rich, lean the main jet size one at a time until the smoke ring at the base of the porcelain is a light brown. If the porcelain base is white, don’t run the engine and contact CT. If the plug color looks good, continue riding at a race pace for ten minutes. Stop and let the engine cool. Check the torque on the cylinder base and head nuts.
9) More on jetting. If you generally run your engine flat out in sixth gear then make your jet pass/ plug shop in sixth. Motocross jetting is checked in fifth gear, therefore it is not safe to run MX jetting in the desert or down a road wide open in top gear. Desert jetting is richer than MX jetting. When running an engine at full throttle for extended periods be sure to chop the throttle decisively to slow down, just rolling out a little can seize a well jetted engine.
CT racing 11805 E. Slauson Ave. Santa Fe Springs, Ca. 90670 ph. 562.945.2453 fx. 562.945.7006

[TRX-330]

If i was good with jetting i would try to help you on your problem, BUT im still learning jetting myself. I have learned that so far it is a guessing game, go up and it runs worse, then go to the size smaller you had first. Its just a pain and takes time to dial it in perfect. But i do know that the guys on here are very helpful with anything.

[JohnT_98300EX]

The stumble has gotten a bit better. Engine builder did not have the carb straight up and down, was tilted to the left as looking from the rear. Now have it straight up and down and it is better. Can't wait to get it broken in and tuned. It feels a bunch better already and I am taking it easy.

[TRX-330]

Man dose it sound more beastly with the 80 over? I have an engine with an 80 over but it dosent run yet, it rotates but wont run. I think its the timing chain, havent had time to tear it apart yet.

[JohnT_98300EX]

TRX, funny you should ask. It DOES sound better. this is a different animal. And I'm not touching the upper 1/3 of the rev range. The torque difference is real noticeable.
Being honest, I am a bit relieved. I mean, the piston kit, cam, bore, and head work, especially the head work were pricey, for me at least. It seems to be money well spent.
But, let's see if it holds up,,,,,, And when it does, I can't wait to see how it runs when I beat it like a rented mule.

[TRX-330]

I try to do the most i can to my engines. I can rebuild them and dial them in pretty good. I have a guy i send all my cylinders and heads for the machine work, but other then that i do the rest. Man when i had my web cam it ran better then ever, i noticed more with a cam than i high comp piston. I plan to rebuild the 80 over and send the head out for port and polish work, im also gonna get a stage one hot cam for it. I hope it runs with the 400's when im done with it.

[ss420ex]

hey jake, i was planning on comming out this weekend to bring u my 300ex. i'll call ya and let ya know exactly whats going on, and if u have time to squeeze me in your garage.

[TRX-330]

I always have time haha, and i work nights now and dont work on sunday so i have time to do it.