Magneto muncher

breno

breno

New Member
Hi all again,

Ive attached some pics of my magneto muncher.
Its a grubbee 70cc skyhawk with a 18mm mikuni and a dirtbike pipe with the usual top end mods.
Im now onto my 3rd magneto in less than 500kms.
I replaced the CDI aswell the 2nd time the magneto was replaced but sure enough another one went.

I usually ride the bike up in the top end of the rev range as it has a 44 tooth and the right setup for it.

Is the chinese magneto crapping out due to excessive high revving?
I wouldnt think so, as there is a fair few MB's getting around on here which have been modified further than mine, that dont seem to come across this prob too much.

There is no trace of oil in the magneto housing or whatever its called..

Has anyone worked out a fix or replacement for the ignition system yet that is proven to work better than the china sys.?
 

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What are you doing with the white wire?
Just cut it off right at the Mag, you can kill the motor by just grounding the blue wire with the button.
 
bubba said:
cheeky bastard.... 196W... i need to do that on my kit. anything over 200w is illegal here.
Click to expand...
haha thanx 196W is just a random but the bore and stroke is off a 49cc i think.
cost me 22bux from an industrial engraver here in syd.



KC the white wire just has a bp connector on it at the moment isolating it from the frame.
But yeah I think i'll cut it off anyway no need for it really.
I read somewhere on the grubee site that we are supposed to sand back the back side of the armature before fitting up a replacement magneto to get a better earth or something. Havent done that yet either so thats on the list too.

Out of interest though what ohms are youse getting between the black and blue wire I seem to be getting 270ohms off a brand spanker is that lowish compared to some??
 
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Hi Breno,

The old style Magneto has six holes, four are used to bolt the magneto down.

The new style only has the four bolt holes.

Also the new style magneto's have a date printed on the windings.

My Grubee GT-5 and GT2B magnetos both measure 330 Ohm's resistance

between Blue wire and ground.

The Grubee manual says 320 to 340 Ohm's.

It might pay to download the GT-5 manual, it shows the difference between

the old and new magnetos.

Here is an E-bay link for the new style Magneto.

http://www.ebay.com.au/itm/130597982835?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

Regards,
DaveM.
 
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Thanx for the link DaveM.
I think the ones I must be buying are his old stock as they have 6 holes and only measure 265ohms.
The magneto with the 6 holes in there now is already starting to pack it in after no more than 4hrs of riding.

The higher resistance mag's put out more current right?

Im using the stock spark plug that comes with the kit which is a Z4JC and has 3 prongs.
Whats the ideal plug for our climate?
Id say the motor may be running a bit hotter now since I put exhaust wrap on the pipe aswell.
 
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Hi Breno,

I read on this site some-ware that the new style magneto is a definite

improvement.

It even looks to have fixed the problem with the poorly soldered earth wire.

It is now riveted.

Other here might be able to tell you if the higher resistance puts out more

current.

I don't know, I am a self taught amateur and am still learning.

Have you changed your plug wire?

I bought 7mm copper core plug wire off the roll from my local auto spare

parts store, very inexpensive I think i might have paid around $7 for one

meter.

I am still using the original spark plug boot, I am not going to change as it

has been reliable, almost 12 months use.

Get rid of the stock Z4JC plug they are crap!

None of the 3 prongs on the two plugs I have are the same distance from

the center electrode.

I started by using NGK BP6HS plugs but am now using BP5HS, one heat range

colder after someone on this site recommended it for use at sea level, which

I am in Adelaide.

My bike now seems to start easier and runs better.

Regards,
DaveM.
 
Cool, thanks again mate.

Ive replaced the spark plug lead already. Looks like the new style magneto and the BP5HS spark plug is now on the list of things to do.

The electrical side of these things appear to be pretty poor and there isnt a whole lot we can do about them to date.

Hopefully the new mag. and plug will give a better spark and last longer.

cheers
breno
 
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