The pursuit for a brown sparkplug
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https://imgur.com/gallery/wFEtwC6
Alright so I have now made a basic Air restrictor. As you know my DT is running slightly lean with a 320 main jet. Probably due to the fact that the airbox is cut open. I now installed the restrictor and for the first time ever she was running really rich.
What should I do?
A: Take out that stupid restrictor and upjet with the top cut out. (I know it's running lean)
B: Install the restrictor, maybe drill a couple of more holes, and downjet.
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@calum drill a couple of more holes or keep as it is?
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@irongamer727 What's your jetting. YOu said it was like 320.
So just knock that down a tad.
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@calum yes 320 now. But I don't want to loose power doing this.. some power decrease is acceptable..
@irongamer727 Yeah, you're not really getting the art of tuning...
Bigger jets don't necessarily mean bigger power.
The pathetic carb you're running is what is letting your engine down. You can only marry up so much oxygen with the fuel. More fuel doesn't mean more air as you simply are not flowing enough air. You need a bigger carb if you want to start chasing that power.
Knocking the jet sizes down won't affect power unless A. You're dangerously lean, or you were already at that sweet spot.
The optimal jetting would be to run the engine as lean as possible without incurring detonation. This would be indicated by the brown tan.
Always Originate, Never Pirate!
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@irongamer727 Yeah, you're not really getting the art of tuning...
Bigger jets don't necessarily mean bigger power.
The pathetic carb you're running is what is letting your engine down. You can only marry up so much oxygen with the fuel. More fuel doesn't mean more air as you simply are not flowing enough air. You need a bigger carb if you want to start chasing that power.
Knocking the jet sizes down won't affect power unless A. You're dangerously lean, or you were already at that sweet spot.
The optimal jetting would be to run the engine as lean as possible without incurring detonation. This would be indicated by the brown tan.
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@calum do you think there will be a big difference in fuel consumption with a 350 jet and let's say 260?
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@irongamer727 not drastic. I would exect significant consumption in incorrect jetting due to poor pwower delivery and optimised combustion losses. Also an increase in carb sizes will result in losses.
@calum yeah it's mainly for the fuel consumption and the hassle of fitting a new carb that stops me from doing it. I'm essentialy only after a strong, reliable DT. I won't be able to beat my friends gasgas 125 and husaberg etc. Not even with zeel, bigger carb, and a fat exhaust.
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That top pic is lean as looking at the picture it looks melt down lean, does look like its dragging air in somewhere looking at that but also sounds like its overfueling at the topend if it wont pull at the topend which is a contradiction on its own. Strange one though as they usually rev on there own if they are dragging air in somewhere.
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You need to start at the bottom and work through mid to top. If u want to improve the guttless bottom remove the snorkel and dial out the bork with experimenting with pilots and the mixture screw till u get it sweet take no notice of people who say dont, that just because they cant set it up. Then move to the mid with the needle stock seems ok. The main only comes into play at 3 quarter throttle anyway.
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You need to start at the bottom and work through mid to top. If u want to improve the guttless bottom remove the snorkel and dial out the bork with experimenting with pilots and the mixture screw till u get it sweet take no notice of people who say dont, that just because they cant set it up. Then move to the mid with the needle stock seems ok. The main only comes into play at 3 quarter throttle anyway.
@scrimsmustang she runs mint and lulls hard up to 3/4. That's when nothing really happens.
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The Aprilia RS 125 SP, or Aprilia AF1 125 Sport Pro run a Dellorto PHBH28 RD 28mm carb. This carb together with a Gianelli exhaust, gives more than 2HP extra power over the 34mm carb version! More than 35hp at rear wheel...
The DT 200R makes 33 bhp and uses a Mikuni TM28SS carb so do not always need a bigger carb for more power, but a well set up carb with jetting spot on 100%. -
The Aprilia RS 125 SP, or Aprilia AF1 125 Sport Pro run a Dellorto PHBH28 RD 28mm carb. This carb together with a Gianelli exhaust, gives more than 2HP extra power over the 34mm carb version! More than 35hp at rear wheel...
The DT 200R makes 33 bhp and uses a Mikuni TM28SS carb so do not always need a bigger carb for more power, but a well set up carb with jetting spot on 100%.@2stroketerry The RS's quoted to make 33BHP ran the VHSB carb. They later restricted the bikes to 26 BHP and used the PHBH.
I don't know the models which used the VHSB, but certainly the SP would have.
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Small update, fitted my restrictor and landed on a 270 main. She runs better than ever. Sadly I lost my kickstart nut during testing.
Funeral held tomorrow.
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Small update, fitted my restrictor and landed on a 270 main. She runs better than ever. Sadly I lost my kickstart nut during testing.
Funeral held tomorrow.
@irongamer727 Standard, yeah either loctite it or make sure it's properly tightened.
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Small update, fitted my restrictor and landed on a 270 main. She runs better than ever. Sadly I lost my kickstart nut during testing.
Funeral held tomorrow.
@irongamer727 lol rip mr nut
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The Aprilia RS 125 SP, or Aprilia AF1 125 Sport Pro run a Dellorto PHBH28 RD 28mm carb. This carb together with a Gianelli exhaust, gives more than 2HP extra power over the 34mm carb version! More than 35hp at rear wheel...
The DT 200R makes 33 bhp and uses a Mikuni TM28SS carb so do not always need a bigger carb for more power, but a well set up carb with jetting spot on 100%.@2stroketerry said in [The pursuit for a brown sparkplug The Aprilia RS 125 SP, or Aprilia AF1 125 Sport Pro run a Dellorto PHBH28 RD 28mm carb. This carb together with a Gianelli exhaust, gives more than 2HP extra power over the 34mm carb version! More than 35hp at rear wheel...
The DT 200R makes 33 bhp and uses a Mikuni TM28SS carb so do not always need a bigger carb for more power, but a well set up carb with jetting spot on 100%.
33 at the crank maybe no way at the rear wheel lol, a crm125 makes 29 but even after a dynojet session the best ive seen is 21.4 at the wheel on the dyno. 21.4 is about what an old 89 DTR makes at the crank lol. A well setup carb is good
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Small update, fitted my restrictor and landed on a 270 main. She runs better than ever. Sadly I lost my kickstart nut during testing.
Funeral held tomorrow.
@Irongamer727 This may be of interest to ya???
http://www.ngksparkplugs.co.za/technical/technical-spark-plugs/
