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2 Stroke rev problems


Zircon
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Hi guys Zircon here again , so after about 6 months of enjoyable riding my bike has begun to die on me again. Its recently had a new Cylinder ( 70cc as it was the only one available at the time )

After fitting the new piston and cylinder, it ran fine for about 3 months , however it started "spluttering" around 6-7K revs , it would have a bit of a moan but it would come out the other side and continue to rev freely . This has slowly got worse and worse to the point where it only revs to about 7k revs in neutral and about 5.5k when in gear.

I decided to have a look at the old piston , it was fine, but it had allot of black carbon deposits on top , the plug always seemed to be very oily , even after having the pump adjusted at a garage . I fitted new rings just to be sure but still the problem persists.

I've been told it may be the Crank seals pulling though oil from the transmission , just wanted to know for sure before I spent allot of money on labour ! She's always smoked allot too ( white smoke ) but apart from that she's been as sweet as a nut .

Any help is greatly appreciated :)

Just frustrating not being able to enjoy my bike while we have weather like this !

Thanks Again guys .. ( and girls )

hope to out there again with you lot before long ....

Zircon

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Hi guys Zircon here again , so after about 6 months of enjoyable riding my bike has begun to die on me again. Its recently had a new Cylinder ( 70cc as it was the only one available at the time )

After fitting the new piston and cylinder, it ran fine for about 3 months , however it started "spluttering" around 6-7K revs , it would have a bit of a moan but it would come out the other side and continue to rev freely . This has slowly got worse and worse to the point where it only revs to about 7k revs in neutral and about 5.5k when in gear.

I decided to have a look at the old piston , it was fine, but it had allot of black carbon deposits on top , the plug always seemed to be very oily , even after having the pump adjusted at a garage . I fitted new rings just to be sure but still the problem persists.

I've been told it may be the Crank seals pulling though oil from the transmission , just wanted to know for sure before I spent allot of money on labour ! She's always smoked allot too ( white smoke ) but apart from that she's been as sweet as a nut .

Any help is greatly appreciated :)

Just frustrating not being able to enjoy my bike while we have weather like this !

Thanks Again guys .. ( and girls )

hope to out there again with you lot before long ....

Zircon

And the last time you decoked the pipe?

The last plug change

Did you re-jet for the big bore

What condition is the air filter

Have you had to top up the gearbox

How much oil is in the gearbox

Does it start ok

If it starts ok do you need choke, only on cold days or all the time even when the motors hot

Just a few questions before you get carried away with ideas of crank seals. They are not nearly as unreliable as people seem to believe.

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And the last time you decoked the pipe?

The last plug change

Did you re-jet for the big bore

What condition is the air filter

Have you had to top up the gearbox

How much oil is in the gearbox

Does it start ok

If it starts ok do you need choke, only on cold days or all the time even when the motors hot

Just a few questions before you get carried away with ideas of crank seals. They are not nearly as unreliable as people seem to believe.

The pipe has been do-coked ( only 6 months old anyhow )

The Jets have been increased to compensate for the increase in capacity

Changed the plug a week ago to see if that was the problem

New ( and oiled )air filter

The bike starts on the button first time very time. and runs perfectly up to 5.5k revs ( starts without choke .... just a little harder to start )

ill take a look at the gearbox oil tomorrow before work, but i changed it around 4-5 months ago and it seemed fine then .....

Thanks for the fast reply :) Hope this helps

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What condition is the spark? A big blue jobbie you can hear clicking, you say she wont rev? any pops bangs smoke etc while she's protesting or just no rpm rise?

I don't normally shoot for the ig system but.......

My gut is saying weak ig coil or maybe a coil braking down.

I could well be a mile out but those answers are not saying crank seals to me, not particularily shouting fuel either.

One last thing, what happens when your riding along if you try and tease the revs up, using tiny bits of throttle following the revs as they ride, rather than the standard 50 technique of wide open :lol:

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What condition is the spark? A big blue jobbie you can hear clicking, you say she wont rev? any pops bangs smoke etc while she's protesting or just no rpm rise?

I don't normally shoot for the ig system but.......

My gut is saying weak ig coil or maybe a coil braking down.

I could well be a mile out but those answers are not saying crank seals to me, not particularily shouting fuel either.

One last thing, what happens when your riding along if you try and tease the revs up, using tiny bits of throttle following the revs as they ride, rather than the standard 50 technique of wide open :lol:

Um she makes a rather horrible noise when she splutters , ( sounds a bit like its miss firing .. i know it cant be as its electronic ignition )

Ive tried teasing the revs up , helps a little , but not much maybe get and extra 500 rpm ?

As for the coil , i read on another forum to hold the ignition cap a few cm form the frame........ and if you see a blue spark the coil etc should be fine .... no idea how accurate this is though ?

i had a quick look at the coil itself ..... does look a bit battered ,,, dont think its ever been changed :\

Thanks for all the help guys, really appreciated :)

Zircon

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Um she makes a rather horrible noise when she splutters , ( sounds a bit like its miss firing .. i know it cant be as its electronic ignition )

Ive tried teasing the revs up , helps a little , but not much maybe get and extra 500 rpm ?

As for the coil , i read on another forum to hold the ignition cap a few cm form the frame........ and if you see a blue spark the coil etc should be fine .... no idea how accurate this is though ?

i had a quick look at the coil itself ..... does look a bit battered ,,, dont think its ever been changed :\

Thanks for all the help guys, really appreciated :)

Zircon

Then i'm inclined to check the pulse coil, and electronic ig can missfire with the best of them.

Can't tell you what the figures should be or where it is, like i said i may be wrong but its where i'd start from your answers.

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Then i'm inclined to check the pulse coil, and electronic ig can missfire with the best of them.

Can't tell you what the figures should be or where it is, like i said i may be wrong but its where i'd start from your answers.

Is the pulse coil the ignition coil ? Ill take it out and have a good look ..... dont think it could be the earth cable do you ?

Cheers again

Zircon

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its no good having 'a good look' mate. you nead to take measurements and compare them to specifications. you will need a workshop manual, a multimeter and the ability to do this ;)

Spent allot of time using multimeter in A level physics so should be able to figure it out :)

The puzzling thing is , on the Workshop manual for my bike it states

PRIMARY COIL RESISTANCE:

0.23 W +20ºC

SECONDARY COIL RESISTANCE:

7.9 W

Forgive me if im wrong but resistance is measure in ohms is it not ?

possibly a miss type ?

Cheers again guys

Zircon

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The only other resistance specifications i could find in the manual was one for the STATOR COIL which is supposed to be 0.4 - 0.6 Ohms at 20ºc

and the CDI which has a charge coil resistance of 0.36 ohms + or - 20 %

( the manual i got is a PDF and i searched for "resistance" )

Cheers

Zircon

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The only other resistance specifications i could find in the manual was one for the STATOR COIL which is supposed to be 0.4 - 0.6 Ohms at 20ºc

and the CDI which has a charge coil resistance of 0.36 ohms + or - 20 %

( the manual i got is a PDF and i searched for "resistance" )

Cheers

Zircon

Hmmm not sure what they mean by stator coil, theres usually several coils in there. Anyway you might as well check them as far as you can, the charge coil is ignition related (sometimes called source coil) search for coil in your PDF, note down all you find relating to resistance checks including the ignition coil, also note any reference to wire colours for the checks and away you go.

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Just got the Coil off the bike and it looks like the original coil , the resistance seems to be almost double what it should be ( according to the manual )

Primary coil was 0.3 - 0.4 ohms

and the Secondary Coil was 13.3 Kilo Ohms

Ive found a replacement here http://www.wemoto.com/bikes/MBK/TZR_50_X-Power/03-09/picture/Ignition_Coil

Although this looks completely different to mine which looks more like this

http://cgi.ebay.co.uk/YAMAHA-TZR50-TZR-50-2004-IGNITION-COIL-3856_W0QQitemZ180627528819QQcmdZViewItem?rvr_id=222574873283&rvr_id=222574873283&cguid=c491523612d0a0aa15238c33ffd15494#ht_971wt_905

Dunno if this orange one would still work , as the screw holes i think are the earthing terminals for the coil ( on the original one ) unless it just has the wrong picture

Thanks For all the help guys ... saved me allot of time and stress !

Zircon

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Just got the Coil off the bike and it looks like the original coil , the resistance seems to be almost double what it should be ( according to the manual )

Primary coil was 0.3 - 0.4 ohms

and the Secondary Coil was 13.3 Kilo Ohms

Ive found a replacement here http://www.wemoto.com/bikes/MBK/TZR_50_X-Power/03-09/picture/Ignition_Coil

Although this looks completely different to mine which looks more like this

http://cgi.ebay.co.uk/YAMAHA-TZR50-TZR-50-2004-IGNITION-COIL-3856_W0QQitemZ180627528819QQcmdZViewItem?rvr_id=222574873283&rvr_id=222574873283&cguid=c491523612d0a0aa15238c33ffd15494#ht_971wt_905

Dunno if this orange one would still work , as the screw holes i think are the earthing terminals for the coil ( on the original one ) unless it just has the wrong picture

Thanks For all the help guys ... saved me allot of time and stress !

Zircon

Let us know soon as if it fixes it, posts like this can really help others. Hope it sorts it for you.

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Dont forget that sometimes bikes are fitted with resistor type spark plug caps, these have a LOT of resistance and you need to check the secondary with this removed if it is one of those. If your bike has a plug without an 'R' in the number it may well have one of those. You shouldnt be using a resistor plug as well as a resistor cap, just one or the other.

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Just tested it again with the cap off , primary coil still reading 0.4 ohms

Secondary coil now reads 8.09 K ohms

The bike uses BR9ES plugs.... and an NGK cap .. don't know if that helps .

Cheers,

Zircon

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Well I always thought it was on or the other, someone correct me if i'm wrong. What does the manual say about plug type and cap type.

I would fit whatever plug the manual says and if thats an 'R' type fit a cap without resistor.

Still not sure if this is related to your problem though as you had it running well with this combo ?

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