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Old 11-27-2006, 04:32 PM   #1126
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Originally Posted by M7H
And, do you have the engine yet?....

I have no bad experience with the engine to share with you.
I have 2 ZX21 DSII engines, 1 brand new, still needs to be broken in, and 1 older one which is 5.5 liters of fuel "old" now, of which I'm going to replace the rod when the new season starts.

Even though these engine don't have a lot of "pinch" when new, the engine still has the same amount of pinch after 5.5 liters as it had after break-in.
Yes I have the engine. I haven't started breakin yet though. Thanks for the feedback. I was just a little gun shy about the motor because I ran a DSI for about 4 races during the summer. Changed the rod after breakin and it snapped the rod a half gallon after that. I've heard that has been corrected with the DSII.
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Old 11-28-2006, 01:17 AM   #1127
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Ok, fair enough......
Good luck with the engine then......
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Old 11-28-2006, 05:50 AM   #1128
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Originally Posted by dj apolaro
It sounds to me like your head clerance.
I haven't touched the head shims, i was under the impression in the instructions that they were correct for 16% nitro etc

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Old 11-28-2006, 02:24 PM   #1129
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Old 11-28-2006, 02:39 PM   #1130
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When it runs ok the first few minutes, but when heated up properly, starts to bog down, I think your bottom end is to lean.......
Because the composite carb. needs more time to heat up then the engine, people start to tune the engine to fast, first let it heat up properly, then start tunning, not earlier....
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Old 11-28-2006, 02:39 PM   #1131
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Originally Posted by M7H
Ok, fair enough......
Good luck with the engine then......

Started breaking today and everything went smooth. 7 tanks, no flame outs, #7 plug on 30%. Thing motor is very smooth, not peaky like the DSI. It's still on the rich side but from what I could tell once it starts pulling, it keeps pulling all the way to the top end. I like this motor already.
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Old 11-28-2006, 02:44 PM   #1132
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Keep the bottom end on the rich side, and you will not have flame out problems, overlean it, the plug will damage and the engine will change into "flame out mode"
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Old 11-28-2006, 03:01 PM   #1133
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Old 12-01-2006, 07:13 AM   #1134
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Quote:
Originally Posted by M7H
I use the "Josh Cyrul" methode.......
http://www.cefx.net/tips/nitro/break-in/index.php

With a small change in this procedure, to speed it up a bit.....
- preheat engine with hairdryer
- run the engine full throttle (yes very rich) on the startbox for 3 tanks.
- cool down (15-30 Minutes)
- another 2 tanks full throttle
- close the main needle 1/2 turn
- 1 tank of throttle blipping (3 seconds idle, 3 seconds full throttle, 3 seconds idle,......)
- cool down (15-30 Minutes)
- hit the track with a leaner setting that the car will move, change your clutch to early engagement, otherwise you will burn the clutchshoe.
Now on every tank I lean the engine 1/8 of a turn, until it reaches the perfect mixture....

Should be there after 1 liter of fuel (about 1/3 of a gallon)....

A Mega engine doesn't have this huge pinch like a Nova has, so the stress on the conrod and main bearing is way less......
Changing conrod after break-in therefor is not neccesary in my opinion, I change them every 5 liters or so (1.5 gallon)
(Yes I will now change the conrod in my Mega, but the next time I will drive it will be somewhere in Feb/Mar next year, season is over now.....)

Also RickV from Mugen/Ninja shares this idea.....
http://www.rcjracing.com/e107_plugin...php?content.45
Hi M7H, i just bought a ZX21 DS2 and want to follow ur break in method...
just wondering do u monitor the temp during break in??
do u keep it at certain temp and how do u keep it there??
Thanks
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Old 12-01-2006, 07:37 AM   #1135
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Hi ck960.....

No, I don't really monitor the temp, because due to the amount of fuel flushing the engine, the temp will not be very high... (somewhere around 70 Celcius or 160F)
I even cover the engine with a towel or something to try to get the temps up a bit (watch out for spinning wheels or gears.... )

I also want to tell you, that according to the Cyrul methode "richening the engine until it flames out and then go back 1/4 turn on the HSN", might not work properly because it then rev's very unstable on full throttle, I choose the riches as possible setting, but so that the engine revs steady......
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Old 12-01-2006, 07:42 AM   #1136
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Thanks for the info... i'll be running it this weekend
Hope everything goes well...
thanks,
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Old 12-01-2006, 08:20 AM   #1137
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1 more thing....

The DSII comes with 0.4mm of head clearance (or 0.5)
check the amount of head shims, I run both my DSII's with 0.6mm (1 still needs to be broken in....)
0.4mm gives you more bottom, which is for smaller tracks, 0.5 or 0.6, gives more top end, but a little less bottom....

0.4mm on the tracks I run, might give detonation....
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Old 12-01-2006, 08:50 AM   #1138
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Quote:
Originally Posted by M7H
1 more thing....

The DSII comes with 0.4mm of head clearance (or 0.5)
check the amount of head shims, I run both my DSII's with 0.6mm (1 still needs to be broken in....)
0.4mm gives you more bottom, which is for smaller tracks, 0.5 or 0.6, gives more top end, but a little less bottom....

0.4mm on the tracks I run, might give detonation....

I'm running .54mm on mine. Medium track and bottom end is enough for me. That .4mm sounds about right out of the box.
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Old 12-01-2006, 10:32 AM   #1139
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Quote:
Originally Posted by M7H
1 more thing....

The DSII comes with 0.4mm of head clearance (or 0.5)
check the amount of head shims, I run both my DSII's with 0.6mm (1 still needs to be broken in....)
0.4mm gives you more bottom, which is for smaller tracks, 0.5 or 0.6, gives more top end, but a little less bottom....

0.4mm on the tracks I run, might give detonation....

My DSII came with .5mm out of the box. It does give more bottom end power than .6mm clearance. With .6mm and 30% fuel it is a little soft. I've had to work on the clutch and gearing to get it to pull harder out of the turns. I think I might try .55mm the next time out to get that happy medium.
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Old 12-02-2006, 06:25 AM   #1140
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Quote:
Originally Posted by M7H
1 more thing....

The DSII comes with 0.4mm of head clearance (or 0.5)
check the amount of head shims, I run both my DSII's with 0.6mm (1 still needs to be broken in....)
0.4mm gives you more bottom, which is for smaller tracks, 0.5 or 0.6, gives more top end, but a little less bottom....

0.4mm on the tracks I run, might give detonation....
Thanks for the advice, mine comes with 0.5 shim, so i think i'm ok, my local track is not that long, just medium and with tight u turn... maybe will try with 0.4 head shim cos i'm only using 25% nitro... is it adviseable??
thanks
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