Author Topic: Will I need to rejet?  (Read 1467 times)

Frog

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Will I need to rejet?
« on: July 06, 2007, 07:30:08 PM »
Hi  everyone

I would welcome some advice - I have put a less restrictive (OKay.....you can see through it!) can on to my skorpion sport - sound absolutely gorgeous!.

Do you think I will need to up jet?  if so any thoughts?

Cheers

Frog

bullet350

  • Guest
Re: Will I need to rejet?
« Reply #1 on: July 06, 2007, 09:04:38 PM »

almost certainly. i put a straight through pipe on my skorpion sport, and on standard jetting it ran a fair bit hotter than before. i put the standard can back on so i wouldn't have to rejet.

be careful as without rejetting you run the risk of doing some serious damage to the motor.

having said that i'm sure i found a dynojet kit was available for the skorpion (xtz660 anyway), and it did sound good with the pipe.

350bullet

Ian

  • Guest
Re: Will I need to rejet?
« Reply #2 on: July 06, 2007, 10:23:59 PM »

having said that i'm sure i found a dynojet kit was available for the skorpion (xtz660 anyway), and it did sound good with the pipe.

350bullet

Dynojet kit is a ripoff !
It consists of two drills a weaker spring and a needle for around 50 + quid.

The drills are for opening up the main jet as you can't buy bigger jets ,If you want the sizes I'll dig them out . ( yes I bought one )
If you cut a few turns off your spring you get the same effect , secondary carb opens slightly earlier or you can do it with the adjuster screw.

Frog

  • Guest
Re: Will I need to rejet?
« Reply #3 on: July 07, 2007, 10:38:01 AM »
Cheers XBRMZ  I'd apprecaite the sizes of the drills and needle - advice on what I would be doing would also  be great. The dynojet kit is a rip off. Holeshot in the US do a similar kit for $26 which is a lot more like it - BUT no response to my emails:-(

Can is staying on as the bike did feel rather strangled by the original exhaust this may help it rev a little better and free up a couple of ponies.....

Frog

bikeseamus

  • Guest
Re: Will I need to rejet?
« Reply #4 on: July 07, 2007, 11:25:54 AM »
Frog

   You are in luck.  The guys who know the most about tuning MZs live right in the UK. Slipstream Tuning. Their phone number is 01732 743 248.
                                       My MZ Traveller did well with 4 1/2 turns out on the mixture screw and one inch cut off the secondary slide spring with a homemade K&N air filter and an iridium spark plug, which I now swear by. My stock muffler got the 3/4 ' spike treatment.  Bet I gained five horses.
                                                                              Call Slipstream.  They're the best. They can probably tell you which numbered drill size to use on your primary main jet, too, if you need to actually increase its size.  You may not.... keep in mind that richening up low speed jets/mixtures will also fatten the mixture on top. All carb circuits/jets contribute to mixture at higher RPMs.
                           If you aren't experiencing small backfiring through the exhaust when you chop the throttle off on decelleration (fully warm engine) then you are probably rich enough.
                                                                                                    Read the spark plug. It never lies.

  Over on this side of the pond, BP/Amoco Clear 93 octane runs cleanest of all the fuels available to us. It is Alaskan Crude that has been refined to within an inch of its life, and the additives don't junk up the combustion chambers and plugs.

  I won't use anything else.             Soak the secondary carb diaphragm in ATF for 24 hours while you're in there.

  Good luck.
                                                                                                           

Ian

  • Guest
Re: Will I need to rejet?
« Reply #5 on: July 07, 2007, 11:09:08 PM »
Drill sizes are 1.8mm and 1.9mm ,there isn't a number on the needle ( top secret ? maybe)
If your not far away from the Midlands you can borrow the drills ,but I would get spare jets from BSA regal first just in case..
About £9.00 each.

My Skorpion ,
102mm high compression piston ,Raptor heavy duty con rod, Stage 1 hot cam ,TDM CDI ( no rev limit ) ,Blue flame twin port can ,
16 tooth front sprocket , K & N cone filters (soon to be replaced with a proper air box ) ,
Standard jets in carb with dyno jet needle ( carbs not 100% yet )............

Slipstream are the people to talk to ,But watch their prices .  http://www.teamslipstream.co.uk/
Raptor parts can be used to achieve the same results for half the price......................

bikeseamus

  • Guest
Re: Will I need to rejet?
« Reply #6 on: July 08, 2007, 10:23:37 AM »
Mr XBRMZ

   Did you retain your tach functioning when you plugged in your TDM Box? I have a 2001 Traveller and a Carillo Rod I will install this Winter with a nastier piston, and heard there was a wire I need to connect or disconnect to retain my electronic tach function.  Know anything about that?            Thanks.

Frog

  • Guest
Re: Will I need to rejet?
« Reply #7 on: July 08, 2007, 11:37:01 AM »
Thanks for all the advice

Two Questions - one for Bikeseamus and one for XBRMZ

Bikeseamus - was it the mixture on the primary carb you enriched with the mixture screw?

XBRMZ - which drill is for which jet?

Cheers

Frog

Ian

  • Guest
Re: Will I need to rejet?
« Reply #8 on: July 08, 2007, 04:55:47 PM »
Hi Bikeseamus ,

RE : TDM CDI , If you have the right CDI with the magic code 3VD on it ,it's plug and play .
If the code is different you've got one with a rev limit .

Hi Frog ,

The main jet is in the secondary carb, right hand side when you sit on the bike .
Which is accessed from the bottom of the carb, It lives above the brass plug.
Both drills are for the same jet ,First drill changes it from 165 to 180 2nd drill 180 to 190.

I've been looking for this since your first post , You might want to try it .
I nicked this ages ago off a website ............. I am not responsible for it ..............
The only problem I can see with it is the possibility of the mixture screw falling out !!


carb modifications. The mixture screw gets backed out(holeshot performance recommends 7 1/2 turns out from lightly seated),the main jet isn't adjustable,
 you replace the 130 main jet from the left side (as you're sitting on the bike)carb with a Keihin 135 and screw it in all the way tight.
The midrange jet needles (both sides) get raised 1 notch, (this means the circlip goes in the second groove from the pointy end)
cut 2 coils from the constant velocity slide spring (right side)and re-install cut side down. Be sure to line up the diaphragm correctly,
there is a little tab on the edge of it that fits into a recess cast into the top of the carb.

The sync screw on top of the carb bank
controls the point after the low speed carb carb starts opening that the high speed carb begins to open,
crank it in a turn or two so that as you twist the grip, you'll feel the free play take up,
then the low speed carb start to open, then the added resistance of the high speed carb opening.
You want the high speed carb to open just after the low speed opens,
 without as much of a delay as with the stock setting. This obviously needs to be set with the carbs reinstalled on the bike before the gas tank is replaced.
Lastly,
if yor bike is a Skorpion (Sport, Traveller, Replica Etc., not a Mastiff, Black Panther Etc.) Remove the black rubber snorkel from the top of the airbox.
Of course, all these modifications are recommended for closed course, racetrack use only. Wink.


Sounds a bit like what Bikeseamus has done to his Traveller.

Frog

  • Guest
Re: Will I need to rejet?
« Reply #9 on: July 08, 2007, 05:04:53 PM »
Cheers XBRMZ That looks like the  plan then!!

I'll give it a go and report back.........

Thanks again

Frog

Frog

  • Guest
Re: Will I need to rejet?
« Reply #10 on: July 08, 2007, 05:49:13 PM »
Just to check before I start - it is the  mixture screw on the secondary carb (right hand side) that I am turning out ??

Sorry - may be a dumb question but I want o get this right!

Cheers

Frog

Steffan

  • Hero Member
  • *****
  • Posts: 1412
Re: Will I need to rejet?
« Reply #11 on: July 08, 2007, 06:49:59 PM »
Possibly not. I fitted a Renegade to mine and I had just reset the carb to stock settings on the original silencer and I haven't had to touch the carb - bike runs better than before. So don't go rushing out until you've tried it.

Steffan

Ian

  • Guest
Re: Will I need to rejet?
« Reply #12 on: July 08, 2007, 07:08:35 PM »
Frog ,

Left hand side as you sit on it ,petrol tap side ....

Haven't you got a manual ?
I've got a SZR 660 manual in PDF format same engine and carb .
post your email address if you want a copy .

Frog

  • Guest
Re: Will I need to rejet?
« Reply #13 on: July 09, 2007, 12:48:32 PM »
Hi xbrmz

No I did not have a manual but just found one here:

http://www.dethlefsens.dk/download/Yamaha_SZR660_Service_Manual.pdf

which is a great help:-)

Thanks to You, Steffan and Bkeseamus and bullet350 for all the advice.

I'll see how I go and try the plan as outlined by Bikeseamus if running  hot or lean.


Cheers

Frog



Ian

  • Guest
Re: Will I need to rejet?
« Reply #14 on: July 09, 2007, 05:47:47 PM »
That's probably where I got it from in the first place ....

Must be getting old ,memory is failing.......

Let us know how you get on , best of luck........