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db4 Dynojet kit

 
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Fri May 30, 2014 4:03 am    Post subject: db4 Dynojet kit Reply with quote

I'm looking at installing a Dynojet stage 2 kit to my stock db4 carbs. The Dynojet website doesn't list a kit for the db4. They list a kit for db2 and quite a lot of Ducati's including 900SS and late and early Monster 900's.

Each of the kits has different jets and needles. I assumimg this is due to the different airbox designs on the different machines.

So, my quandry is which kit to buy for the db4???
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'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Fri May 30, 2014 4:20 am    Post subject: Reply with quote



900SS - This is probably the one i would pick unless somebody knows better?




db2 kit




Late model M900 Monster




Early model M900 Monster.


Anybody got any advice?
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'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
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2bims



Joined: 03 Apr 2010
Posts: 7289

PostPosted: Fri May 30, 2014 8:07 am    Post subject: Reply with quote

basically same engine in Db2 as in the DB4........and youre running an open larger diameter exhaust can arent you BRian? So is your airbox standard or do you have K&N Cone air filters direct onto your mikuni carbs?

I'm sure DeeBee4 will be the one to ask here.....I wouldnt go too extreme on the Dyno kits...as I presume your bike hasnt had any head work done to it...standard bores, cc and cams?

Drop dynojet a line and let them know your location...as you live in a pretty warm country...and shouldnt have issues with cold running so should be less of a compromise in jets/needles etc.....
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vort28



Joined: 22 Mar 2010
Posts: 2194
Location: Northwest , UK

PostPosted: Fri May 30, 2014 11:33 am    Post subject: Reply with quote

They are US ones, wont they also be different due to emmission regs ,engine output ? Do they have the same jets/carbs to start with ?
I would go for the last kit available for a Euro 900ss carb engine.

Have you sorted the intermittent running issue out for the 4 now Brian ? or is this part of the plan ??
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Evilchicken0



Joined: 12 May 2010
Posts: 2996
Location: London

PostPosted: Fri May 30, 2014 11:48 am    Post subject: Reply with quote

A dynojet kit is just a set of needles and jets - you can do the same thing with the standard ones ... just put it on a dyno
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Corona



Joined: 26 Jun 2008
Posts: 118
Location: Norfolk

PostPosted: Sat May 31, 2014 12:18 pm    Post subject: Reply with quote

A good start is to go by the date of engine manufacture, then it's carb model and standard jet/needle sizes. If you can get a dyno as it is it can show up any issues and or improvements you can make and tailor the power output to your desires within reason. You are robbing Peter to pay Paul with these kits, sacrificing driveability for peak power to an extent, best quiz those that race this model and seek advice on base settings before you commit to a particular kit.
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Hursty



Joined: 29 Aug 2012
Posts: 319
Location: New Zealand

PostPosted: Sun Jun 01, 2014 8:30 am    Post subject: Reply with quote

Sounds like you need to load both the DB and the SB on a trailer and find a dyno with an operator who knows what they are doing.
Probably the best money you'll spend Wink
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deebee4



Joined: 08 Jan 2011
Posts: 266
Location: Netherlands

PostPosted: Mon Jun 02, 2014 5:57 am    Post subject: Reply with quote

Sorry Brian, I was very busy but I'll get back to you this week.
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Mon Jun 02, 2014 11:37 pm    Post subject: Reply with quote

2bims wrote:
basically same engine in Db2 as in the DB4........and youre running an open larger diameter exhaust can arent you BRian? So is your airbox standard or do you have K&N Cone air filters direct onto your mikuni carbs?

.


Stock db4 airbox and aftermarket exhaust can on mine. Same engine in db2 and db4... thats why i find it strange that the db2 and 900SS dynojet kits are so different?
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'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Mon Jun 02, 2014 11:41 pm    Post subject: Reply with quote

vort28 wrote:

Have you sorted the intermittent running issue out for the 4 now Brian ? or is this part of the plan ??


I don't think i've sorted it yet Stu. I haven't found anything with the electrics. Found a couple dodgy orings in the carbs, have ordered new seal kits for the carbs and thought if i get some dynojet kits i can at least rule out my needles as being dodgy and i'd have a selection of jets to experiment with.
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'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
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bidalot



Joined: 14 Feb 2012
Posts: 75
Location: Paris

PostPosted: Wed Jun 04, 2014 6:13 pm    Post subject: Reply with quote

Hi,

My DB3 (year 1995) wears a Dynojet stage 1.

Needles clips on position 1.

Main Jet YJ 150.

It runs perfectly.
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deebee4



Joined: 08 Jan 2011
Posts: 266
Location: Netherlands

PostPosted: Wed Jun 04, 2014 6:46 pm    Post subject: Reply with quote

Here's some pictures of the needles and springs.

Needles: top = stock, middle = stage 2, bottom = stage 3 (if I'm correct)



Springs: Top = Question, middle = stock, bottom = stage 2



By varying the needles and jets and springs you have a lot of possible combinations. Also you can alter the holes in the slides.
Needles regulate the fuel flow from the float bowl through the main jet and diffuser (needle jet). The springs regulate the amount the slides open at a certain vacuum pressure, on the intake side of the engine.
The holes (with the springs) regulate the responsiveness of the slides.

On the internet I often read people altering needles, but reverting to the stock springs.

Anyway, all that fiddling is one of the reasons I switched to Keihin FCR carbs. Also Mikuni TDMR 40 will perform great. Drawback could be the costs.....
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