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| ZUMIKE |
 Posted: Sun Jul 25, 2010 10:46 pm |
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Joined: 14 Jul 2010
Posts: 42
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If I get a expansion chamber exhaust made for the stock engine, what size jets would I need to get, and do I need a new needle?
looking at a technigas next r for a stock 50cc engine
Well I ordered the pipe, and jets from 85-100 and yellow clutch springs. I read some and saw I need stronger clutch springs, so im just hoping I can get the jets figured out easily. I will start high and work my way down. |
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| 190mech |
| Posted: Mon Jul 26, 2010 4:37 am |
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Joined: 01 Oct 2009
Posts: 99
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| You'll need lighter rollers too,maybe 4-4.5 grams as a starting point.. |
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| ZUMIKE |
| Posted: Mon Jul 26, 2010 8:22 am |
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Joined: 14 Jul 2010
Posts: 42
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I have a whole stage 6 weight pack of all different weights, havent used them yet so I should be good there.
So I probably have to go lower in weights because the new pipe will rev up differently then the stock. I want more rpm before anything engages? I guess this is why you add stiffer clutch springs
Can I run the air box as is, or do I need to take that snorkel plug out? I know if I get it set up and do anything different to the air box I would have to rejet again, so I only want to do this once. |
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| ZUMIKE |
| Posted: Thu Jul 29, 2010 4:34 pm |
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Joined: 14 Jul 2010
Posts: 42
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Well so far im about 99% done tuning. Right now im using yellow contra, 4g weights, stock clutch springs as the yellow were to stiff, so I have other ones coming. Im hoping they will be softer the yellow but harder then stock. Orange and red from stage 6.
New malossi belt.
Ive gained +3 mph full speed. +6 mph on long steep hills, and +2 short steep hill. Acceleration is a tad slow for 1 sec, but the new clutch spring should fix that. Stock air box, main jet 85. 87.5 and 90 was too rich and caused slight bogging. No plug chop yet but coming soon. |
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| StepVino |
| Posted: Thu Jul 29, 2010 6:43 pm |
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Joined: 05 Feb 2008
Posts: 1654
Location: Houston, TX
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ZUMIKE wrote: ..
Can I run the air box as is, or do I need to take that snorkel plug out? I know if I get it set up and do anything different to the air box I would have to rejet again, so I only want to do this once.
Good luck with that  . Seriously, the air box snorkle will restrict
air flow, so ideally you could try replacing it with a larger diameter
90 degree bend of some kind, possibly a copper elbow from the
hardware store.
Next it might happen that your throttle will loose response
past 3/4 open. This will be the rubber elbow from the carb
to airbox restricting flow. You can try fixing that by dremmeling
out the inside of the elbow. After this you should try raising
the needle a notch.
The needle shape should be ok, unless you replace the airbox
with a foam filter. |
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01 Vino, ported Polini sport
05 Vento BKM Jazz stock |
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| ZUMIKE |
| Posted: Thu Jul 29, 2010 8:25 pm |
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Joined: 14 Jul 2010
Posts: 42
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Well I dont want to mess with the needle jet unless I have to , im not really comfortable with removing the carb, im fine changing jets but thats it so far.
What do you think about the new plug #3. This is not a plug chop but just what it looked like after a 30 min hard run.
Some reason now im getting an extra 2mph on hills then earlier today, im wondering if the belt is already wearing showing more performance, and this was at the end of the hard ride and it was hot.
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| StepVino |
| Posted: Thu Jul 29, 2010 9:37 pm |
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Joined: 05 Feb 2008
Posts: 1654
Location: Houston, TX
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It's been a really long time since I played with plugs.
Number 3 looks ok, but there's something not quite
right about the gound electrode. I can't tell if it's too
hot or too cold. Below is a pic of what you would like to
see, as far as heat range. You want the ground electrode
clean down to about half way:
Some good info on plug reading:
http://www.strappe.com/plugs.html
Here is my favorite plug . Check for correct 'reach':
http://www.ngk.com/results_cross.asp?pid=bpr8hix&x=30&y=15 |
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01 Vino, ported Polini sport
05 Vento BKM Jazz stock |
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| jonik |
| Posted: Fri Jul 30, 2010 3:14 am |
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Joined: 11 May 2010
Posts: 21
Location: Finland
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| ZUMIKE |
| Posted: Fri Jul 30, 2010 9:40 am |
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Joined: 14 Jul 2010
Posts: 42
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| Ive seen that site posted above, but all those plugs look crusty and old so its hard to match up. Is there a difference in 2 stroke and 4 stroke colors |
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| ZUMIKE |
| Posted: Fri Jul 30, 2010 5:33 pm |
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Joined: 14 Jul 2010
Posts: 42
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Did my first plug chop, but maybe I did it wrong. Had it all warmed up, actually drove to a spot. Swapped plugs to a brand new one. Drove maybe 200 yards full throttle, hit the kill switch. Here is what I got
Now the ground strap is chalky white all the way to the threads, on each side of ground is a brown spot on the thread metal. I can see the whole ceramic and no color on it.
I also did one at 90main jet, same color but the ash color doesnt go all the way to the threads. Thats the only difference.
Now at 90 main it studders during acceleration and doesnt feel right. I have a 87.5, same thing studders and doesnt feel right.
So did I not drive enough? Because to me it looks way to lean. But my 90plug is almost exactly the same. I was under the assumption you just had to drive a little but im wondering if you need to drive for a while. |
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| StepVino |
| Posted: Sat Jul 31, 2010 6:43 am |
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Joined: 05 Feb 2008
Posts: 1654
Location: Houston, TX
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The article I linked to above is by Jennings, on how to read
spark plugs. He mentions that you need several minutes
of running. Personally I've never been able to do that because
of the available roads.
The gray deposits might be something to be concerned about.
Could they be aluminum deposits? I doubt it, but can't tell.
What was the stock main jet size? When you say it didn't feel
right, was that during acceleration, or also once it settled down
to full speed? How did you accelerate, wot from standstill, or
did you gradually open the throttle?
Have you made any changes to the snorkle? |
_________________
01 Vino, ported Polini sport
05 Vento BKM Jazz stock |
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| ZUMIKE |
| Posted: Sat Jul 31, 2010 8:39 am |
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Joined: 14 Jul 2010
Posts: 42
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stock jet is 80
using 87.5, and 90 it stumbles on acceleration, stumbles 1/3 and on deceleration gugrles. I also loose 1mph
the chop was on a 85, right to wot but for a couple hundred yards
I have a better spot im going to try for 1 mile |
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| StepVino |
| Posted: Sat Jul 31, 2010 9:18 am |
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Joined: 05 Feb 2008
Posts: 1654
Location: Houston, TX
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Good luck with your tests. Testing with the 85 sounds like a good
idea, I wouldn't worry about the 1mph less for now.
Unfortunately once you add the exhaust pipe, it makes your
fuel mixture dependent on the tuned rpm of the engine and
pipe, and it gets non linear. If that makes sense. You need
more fuel when you are on the pipe rpm, and less everywhere
else. You definitely want the correct fuel mixture at max
power rpm, but then you'll be rich everywhere else. A common
result is a stumble off idle, which is hard to get rid of without
going dangerously lean.
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01 Vino, ported Polini sport
05 Vento BKM Jazz stock |
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| ZUMIKE |
| Posted: Sat Jul 31, 2010 12:50 pm |
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Joined: 14 Jul 2010
Posts: 42
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Thanks for the info. I did my plug chop, 2 miles wot 42 mph average speed. During the kill switch slowing down it backfired 2 times.
There is no smoke ring, the ring you see is metal
So im guessing this is very lean?
I got around to taking the seat out to access the needle. I raised the needle 1 notch lowered clip. Put in 90 jet. Had the lag at takeoff and lost some top speed ans slightly slower hill speed. Tried 87.5 still small lag at takeoff top speed normal, hill climbing speed normal. Put in 85, maybe a tad hint of a lag, lost 1mph speed and hill climbing speed dropped by 1mph.
So now im going back and raising the needle to the max, and try everything all over again.
If you say stumble is normal then I will accept it when it happens. Plus then I can use a slightly larger jet which should help with the lean condition. |
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| ZUMIKE |
| Posted: Sat Jul 31, 2010 3:21 pm |
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Joined: 14 Jul 2010
Posts: 42
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So ive adjusted the needle twice, both times raising it from stock. All 3 jets I use end up loosing power, and with the higher ones I get a chugging feeling on a short steep hill as the rpm's arent enough. Top speed is around the same, maybe reduced 1-2 mph, and hill climb was reduced maybe 1 mph.
So after all this im back to where I was to start with. +5 on main jet compared to stock and thats it. Needle back to stock location. |
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