is their a rule of thumb for the bored carbs? 33-35.5 carbs do u go up 1 size on the mains and drop the pilots 1, just looking for a bases, i have the rest of my mods figured out but can not figure out what difference is needed for the bored carbs, and the sled seems to be running real rich
99' mm700, peak head 22cc, 1 layer removed from head gasket, gutted box, stock pipe (triples in the garage just not on yet), bored carbs, riding at 8-10000ft around 0-20deg. right now i have 135 mains across the board and 60 pilots.
thanks mike
99' mm700, peak head 22cc, 1 layer removed from head gasket, gutted box, stock pipe (triples in the garage just not on yet), bored carbs, riding at 8-10000ft around 0-20deg. right now i have 135 mains across the board and 60 pilots.
thanks mike
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at that alt you should get smaller domes for the head . i have 22 at 1200 ft
RJH
New member
First:
I would never bore a carb for more performance...well maybe on a 120 sled – it would work.
You would want to go smaller on the mains – as the air speed is slower..... than what it was.
The pilot should not be affected by a larger bore – you have dug into some of the pilot passages - that would probably not change – however – I have never bothered to jet a bored carb.
I would never bore a carb for more performance...well maybe on a 120 sled – it would work.
You would want to go smaller on the mains – as the air speed is slower..... than what it was.
The pilot should not be affected by a larger bore – you have dug into some of the pilot passages - that would probably not change – however – I have never bothered to jet a bored carb.
toydoc
Member
You want to go UP on the main because the air speed slower and it won't pull the fuel up the main as easy (as smaller bore carb). The less vacuum signal you have, more main is needed
9801srx
Member
yep like toy doc said ,with the lower air speed across the main nozzle less fuel will get pulled through the same size main also the larger bore allows a larger volume of air to flow through the carb also requiring a larger main to keep the same a/f ratio.
does any one know how much, the main needs to be changed for the bore change? that is where i am struggling?
INLINE4
New member
- Joined
- Jan 6, 2006
- Messages
- 260
Don't really know about your elavation but sea level to 1800' I always put bigger brass (nozzels) in bored carb for the mid-range..
RJH
New member
It’s not possible to guess jetting on line as every engine, environment and riding style is different. Just give it a high speed run – kill the engine..and check the plugs. You seem savvy on performance – so it should be easy for you to do.
Read what you have said…..IT SEEMS RICH….. so ….you would go down a jet size……smaller. Maybe the high speed air correction was changed – that would make it rich – trying to lean it would seize it. Doubt that thou.
In addition….you have given it more air with the holes in the box …so that would mean it should require bigger jets. – but yet it still seems rich.
I’m not a fan of boring carbs….on a high performance engine and would never waste time trying to jet one. That’s only my opinion.
Yamaha engineers have spent a ton of hours and money getting the resonate frequency to work in the intake track with reeds and carb size. You have changed that – not by much so it should be OK. In addition – the air box is designed with its own frequency - which has been altered with the holes.
It was mentioned to change the emulsion tube – I think your carb has removable ones – but I’m not sure if Yamaha offers different sizes. Again – the sonic wave is greatly changed - so you will have to test to find out.
Other things to look for:
Does the slide stick down into the hole – with the material removed?
Does the manifold match the new carb size?
Does the intake track match the new carb size?
Did he cut too far into the pilot circuit?
Read what you have said…..IT SEEMS RICH….. so ….you would go down a jet size……smaller. Maybe the high speed air correction was changed – that would make it rich – trying to lean it would seize it. Doubt that thou.
In addition….you have given it more air with the holes in the box …so that would mean it should require bigger jets. – but yet it still seems rich.
I’m not a fan of boring carbs….on a high performance engine and would never waste time trying to jet one. That’s only my opinion.
Yamaha engineers have spent a ton of hours and money getting the resonate frequency to work in the intake track with reeds and carb size. You have changed that – not by much so it should be OK. In addition – the air box is designed with its own frequency - which has been altered with the holes.
It was mentioned to change the emulsion tube – I think your carb has removable ones – but I’m not sure if Yamaha offers different sizes. Again – the sonic wave is greatly changed - so you will have to test to find out.
Other things to look for:
Does the slide stick down into the hole – with the material removed?
Does the manifold match the new carb size?
Does the intake track match the new carb size?
Did he cut too far into the pilot circuit?