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Discussion Starter · #1 ·
Excuse me, but I am sort of lost.
Today I went to the mechanic and after few minutes of talking he said that they can make "jetty" or something like that on my engine( please excuse spelling if its wrong). Maybe there was more to the name, but I can't recall it. Now what I understood is that they callabrate your carburetor or something else, and apparently that can improve the perfomance on the bike slightly better. He also pointed out that its more noticable on small engine bikes like my 250. Can someone please explain roughly what it is? And also does removing muffler changes anything apart from boosting the sound?
Thank You :)
 

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Excuse me, but I am sort of lost.
Today I went to the mechanic and after few minutes of talking he said that they can make "jetty" or something like that on my engine( please excuse spelling if its wrong). Maybe there was more to the name, but I can't recall it. Now what I understood is that they callabrate your carburetor or something else, and apparently that can improve the perfomance on the bike slightly better. He also pointed out that its more noticable on small engine bikes like my 250. Can someone please explain roughly what it is? And also does removing muffler changes anything apart from boosting the sound?
Thank You :)
They're talking about "jetting" or adjusting the carbs to provide optimal fuel to the engine. Everything else needs to be up to spec first though - valve clearances, filters, etc.
I wouldn't agree that the size of the engine makes much difference.
Removing the muffler will provide more topend power at the cost of the midrange so is not recommended for road use. It will also make the bike illegal, attract Police attention and piss your neighbours off.
 

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:plus1: That sentense made my day :) I don't know why :) Probably the neighbour part.
But yeh thank You. So overall is it worth "jetting"?
:)
Personally, I like to know that the engine is running at its best so I would ensure the jetting is good.
If your jetting is less than optimal though it's probably due to poor maintenance or worn parts in the carbs.
First, bring everything else back to as new spec as the stock jetting is best suited to when the engine was new - assuming it hasn't been messed with already. New air, fuel and oil filters, fresh oil, fresh coolant, new plugs, ensure there are no air leaks in the intake or exhaust system and adjust everything else to be within spec, particularly the valve clearances. I would also recommend running compression and leakdown tests to ensure the topend is strong to begin with.
If the jetting is still off then I'd open up the carbs and thoroughly clean everything and make sure nothing is broken, worn or perished. Float needles, jets and emulsion tubes are common wear items but slides can also wear and the diaphrams can harden or split.
Synchronise or balance the carbs.
Then, if there are still problems you can look at changing jets, needles, springs, etc.
Your profile shows the CBF250 - is that the Hornet?
If it's fairly low mileage I wouldn't be concerned with jetting yet.
An aftermarket muffler would be a nice start if you're determined to play with it though.
I'm not familiar with the CBF250 but dropping a tooth off the front sprocket might liven it up very nicely. You probably only have 160kph now though and lower gearing is likely to reduce that significantly - depending on how over-geared it is to begin with.
You've probably got something like 30bhp and jetting it isn't going to give you a noticeable increase in peak power but it may improve the midrange to make the bike a little nicer to ride.
I'd recommend just riding it as much as possible so you can make the most of the power you already have.
 

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Discussion Starter · #5 ·
Yeh, I am not sure. The bike has travelled 4,000km, is it long or not for the bikes? Also the mechanic said jetting can improve the way bike behaves in the morning.
I don't think its a hornet, on internet CBF and Hornets are apparently two different things. But yeh he told me I am not going to get like a major boost in power, but I am thinking - if you can improve the power of it, why not do it? :)
Thank you for your advice
 

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Yeh, I am not sure. The bike has travelled 4,000km, is it long or not for the bikes? Also the mechanic said jetting can improve the way bike behaves in the morning.
I don't think its a hornet, on internet CBF and Hornets are apparently two different things. But yeh he told me I am not going to get like a major boost in power, but I am thinking - if you can improve the power of it, why not do it? :)
Thank you for your advice
No, 4000kms is nothing at all. I doubt you'd expect to see any significant losses in performance before at least 50,000kms as long as you keep it well maintained. Regular oil and filter changes and clean air filter are the most vital.
Jetting can adjust the cold-start but shouldn't be necessary. Are you having cold-start problems? Are you letting the engine warm up properly before trying to make it work?
Any chance of a picture? I think the Hornet has a high-mount muffler but I'm not at all familiar with them.
It's always possible to get more power depending only on how much you want to spend.
There isn't a lot of point though if you aren't able to maximise what you already have. If you're currently only using 20hp of your 30 there isn't a lot of sense in trying to boost it to 35hp.
 

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Discussion Starter · #7 ·
No, 4000kms is nothing at all. I doubt you'd expect to see any significant losses in performance before at least 50,000kms as long as you keep it well maintained. Regular oil and filter changes and clean air filter are the most vital.
Jetting can adjust the cold-start but shouldn't be necessary. Are you having cold-start problems? Are you letting the engine warm up properly before trying to make it work?
Any chance of a picture? I think the Hornet has a high-mount muffler but I'm not at all familiar with them.
It's always possible to get more power depending only on how much you want to spend.
There isn't a lot of point though if you aren't able to maximise what you already have. If you're currently only using 20hp of your 30 there isn't a lot of sense in trying to boost it to 35hp.
Sorry having problem attaching URL of the picture of the bike, http://www.fireblades.org/gallery/showimage.php?i=12382&c= , thats the link, or it should be in my profile gallery. Yeh cold starts are pain quite often, as I have to start the engine and sit for at least 30seconds reving it to 3-5rpm, then I can let it go and not fear that it will die. I let it warm up to about 1.3rpm , normal rpm for all ready and warm engine on my bike is 1.5rpm.
Yeh chaning oil filters and other filters is sort of complicated for me, not that because I am bad with working with tools, but because I never seen where they are and how to extract them without stuffing up things. But next time I go to my mechanic, in about 300km I shall ask him to let me watch as he will be doing 4K km check. Sorry for asking but what does hp stands for? Yes, I am a rookie
Thank You :)
 

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Sorry having problem attaching URL of the picture of the bike, http://www.fireblades.org/gallery/showimage.php?i=12382&c= , thats the link, or it should be in my profile gallery. Yeh cold starts are pain quite often, as I have to start the engine and sit for at least 30seconds reving it to 3-5rpm, then I can let it go and not fear that it will die. I let it warm up to about 1.3rpm , normal rpm for all ready and warm engine on my bike is 1.5rpm.
Yeh chaning oil filters and other filters is sort of complicated for me, not that because I am bad with working with tools, but because I never seen where they are and how to extract them without stuffing up things. But next time I go to my mechanic, in about 300km I shall ask him to let me watch as he will be doing 4K km check. Sorry for asking but what does hp stands for? Yes, I am a rookie
Thank You :)
I would expect it to take more than 30 seconds to warm up. You would want to see at least 40C on the temp gauge and 50C would be much better.
Hp is horsepower. Bhp is crank horsepower.
 

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Discussion Starter · #9 ·
Oh no, I explained it wrong. I give it 5-7mins to warm up, but I have to rev it for a half a minute in order for it not to drop lower than 1 and shut down. After a half a minute I release throttle and let it warm itself up for 6 more minutes at least
 

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Oh no, I explained it wrong. I give it 5-7mins to warm up, but I have to rev it for a half a minute in order for it not to drop lower than 1 and shut down. After a half a minute I release throttle and let it warm itself up for 6 more minutes at least
Has it been like this from new?
Something may need adjustment but it doesn't need rejetting for this.
 

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I didn't buy it new. Its a 2007 model, I bought from the second owner in November-December. So yeh its been like that since I bought it
Then I would check all the maintenance is up to date before you start adjusting the carburetors.
 
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