Bike slower when up to temperature, faster when cold.

[sinfull]

Been near a week now Trademe tut tut ! Go buy some new 9's chuck em in and if that dont fix, ride in a higher rev range till ya can afford to do ya carbs !

[klyong82]

Yeah thanks i was thinking of getting from TYGA.

What about those 8's, as opposed to 9's??

Hmm the 8's are hotter plugs so would be more suitable for communting in warm temperatures while the 9's cooler plugs perform better for touring or high performance bikes (1000cc etc).

[racefactory]

Ok just about to make the order from the UK... 90 bucks for a set including shipping, absolute cheapest i could find lol!

[The Pastor]

Sounds like jetting/carb thing... but I won't say any more. Air filter? Shit I don't know...

This engine is EFI ? If it is, then will will be richened right up when its cold, and leaned out as safe as possible towards stoich when its warm, for cleanliness and economy. So yeah you are probably right - maybe its a little lean.

IF this this the problem, you can put a variable resistor on the water jacket temperature sensor and 'fool' the computer into thinking it's colder than it really is, and it will keep it slightly richer for you. Of course you could fuck the engine completely playing with this stuff too, so YMMV.

My ol' skyline was the same - bags of omph while she was warming up and a little laggy while warm. It had a worn throttle body - was leaking air in around the spindle, so maybe you have a similar leak. It also had a big dead spot when warm.

Alternatively there might be a simple fault elsewhere.


DB

are you always this stupid or are you just trying harder today?

ok took the air filter out and had a look... doesnt look that dirty to my eyes but it's the first time i've seen one anyhow. Don't understand how the machine can actually suck any air through that series of sponges though. Don't know how much oil is supposed to be on the sponge either. Shall I try running it with only the little sub air filter element in place? Shall I just put some pantyhose or something over the main air filter gauze and run it as opposed to having that thick sponge blocking the air and see if that makes it better?

I don't understand how it's electronic issue as it goes like a raped ape in cold weather/ warming up engine temperatures.

needles- yes well the problem is at low rpms, suggesting the needles but then again... it runs like a raped ape when it's cold and wouldn't a worn needle jets be shitty when in colder temperatures too?

Surely it's to do with air flow since air is less dense when warm?

One thing to remember here is that it's not exactly a problem in a 'problem' sense lol, it's just something i've noticed... it still goes like mad when it's warming up. It's just I only get, say 10 mins of real good fun before it gets slower and less punch.

apparently fuel tank breather can affect mixture, is that true? What if i run it without that?

I would do this

- change the plugs.
- remove airfilter [not the air box] and run with out it (just to test it)
- get the carbs balanced
if it still running werid i'd see about new needles or a dyno tune.

FYI you can buy air filter foam and cut your own filter to fit - you oil them with 2 stroke oil (cheapest you can get) and you put on sparely - no excess oil

[racefactory]

yeah I agree- well hopefully plugs solves it.

Yeah i don't know what the dude was on about earlier lol!!!

[lankyman]

Lol. No don't think it's lean. Boggy acceleration is not a sympton of lean mixture as far as i know.

No it's not fuel injection it's an NC30.

Thanks.

Another thing to note- when it's up to temp, when you slam on the throttle full blast it is worse, engine note changes to a more burbling, boggy kind of sound. If you roll on the throttle, it seems to be better, still not the best but bit better. So basically you just can't make the revs climb too fast otherwise it will go rich.

I think i've pretty much answered my own question in terms of what's wrong? But it's just a stock bike, what could be causing this?

I've never looked at the air filter, and they are harder than most bikes to get to (like every simple maintenance task on these bikes) so that's why. Don't know if that could cause this though as when it's getting warmish it goes liek hell.

If you pull out the air filter you will see at the front of the air box there is a little rubber flappy thingy that the air has to force it's way around to enter the airbox. If you remove this peice (cut it off) you'll notice you get better throttle response and it won't try to die when you blip the throttle at idle. I've read reports about this causing a pressurisation of the intake but mine has never run better since carrying out this small mod. Also replace the crappy paper filter if this hasn't been done already.

[lankyman]

yeah I agree- well hopefully plugs solves it.

Yeah i don't know what the dude was on about earlier lol!!!

And with plugs being 50 bones a piece, I'm sure this is worth a try beforehand.

[racefactory]

If you pull out the air filter you will see at the front of the air box there is a little rubber flappy thingy that the air has to force it's way around to enter the airbox. If you remove this peice (cut it off) you'll notice you get better throttle response and it won't try to die when you blip the throttle at idle. I've read reports about this causing a pressurisation of the intake but mine has never run better since carrying out this small mod. Also replace the crappy paper filter if this hasn't been done already.

Wow ok, will have to check this out when i get it all apart again when the plugs arrive... Swear i never saw such a thing in there. Surely you'd think Honda would know the best?

[niero]

Its completely normal (up to a certain degree depending on the engine design). Engine performance decreases with drop in HpA (Air Pressure) and temperature. This is truly visible when you fly helicopters. On some days you will not be even able to lift of due to the humidity, and the temperature of air. When the air is colder its also denser. Therefore, if the bike is getting too hot and the air takes time to get in to the engine (depending on the construction of the engine) the air may become less dense (aka less air per fuel ratio) and a RICHER mixture will occur. This will result in power loss and lead deposits in the spark plugs (spark plugs fouling), if the mixture is too lean though, this is by far worst case scenario, things like Pre Ignition and Detonation may occur, very bad for the engine, also if you see that you Cylinder Head Temperature is going through the roof (I doubt you have that instrument but I'l keep going anyway) this is a sign of mixture being too lean. The new engines have CDI's instead of Magnetos, I am not sure what you have but if it is the cdi, the following may also be occurring. in semi conductive circuitry a rise in temperature will increase the resistance in the wire, but will decrease the resistance in your resistors. The resistors serve two purposes (usually), to limit the current and to get rid of the heat. If its resistance is dropping it will mean that it will also become inefficient at getting rid of the heat. Therefore the microchip inside your CDI is getting a bit hot, and sometimes at certain points may shutdown due to heat shock. Dont panic thats ok, most new chips nowdays just shutdown when they are too hot and come back online when they are cool again. in your case its might be just a couple of pins, try giving the CDI some vent, see what happens!

[xwhatsit]

When I had trouble getting a good fat blue spark, this effect used to be very noticeable on my bike. Now it's less obvious, presumably because now with great spark I'm getting good combustion every time even if it's hot (so the mixture is not optimal or whatever is going on). But sometimes, when you wake up really early before it gets light, hunched over the tank down the hill into Kawakawa Bay, you can feel the engine crackling and howling like it never does normally. It loves the cold air, engine feels crisp and sharp. My father reckons it's a thing air-cooled bikes do, but I dunno about that. My guess is carburettion vs. EFI.

[racefactory]

Interesting.

Yes, must be just all carb engines to some extent.

niero... how can I tell if my cylinder head is too hot- what kind of reading should i be expecting?

[niero]

Absolute Max 140 C.Well, here is where you need a sender unit mounted into the cylinder head. Much like your water temp it will be connected to a sender terminal and will transmit the temperature on to a gauge. But this occurs only when too lean mixture is present, when I had an other look at you issue I dont think the mixture is too lean but rather too rich. Are there any carbon deposits anywhere on the spark plugs or anywhere else? A good way to test if its your intake is to go in a 60-70km/h area where you are in your last gear but doing not too many revs, and give it some gas, (when running hot) if she goes well then its your intakes, if not then again it might be Mixture Setting. For the reasons I have stated above the air will be less dense and therefore when ignition occurs there is not enough air to ignite all the mixture (Fire needs oxygen). The only way to overcome that is to ventilate your bike better, get a better radiator unit or make the air intake bigger, maybe even mount a fan in it (talk about "old man's turbo) Good Luck!

[lankyman]

Wow ok, will have to check this out when i get it all apart again when the plugs arrive... Swear i never saw such a thing in there. Surely you'd think Honda would know the best?

Yea you'd think so aye....

[lostinflyz]

Yea you'd think so aye....

mwahahaha by the time youve made it through the manufacturing and budgeting department any good thoughts they have are stripped bare and only the bare essentials left, that were the cheapest, easiest and fastest to make.

however its quite common for guys to modify the airbox on these. so it may never have been there. honda makes motorcycles to last forever and considering jap restrictions on 400cc motorbikes thay could be pretty conservative with the airbox.

[racefactory]

mwahahaha by the time youve made it through the manufacturing and budgeting department any good thoughts they have are stripped bare and only the bare essentials left, that were the cheapest, easiest and fastest to make.

however its quite common for guys to modify the airbox on these. so it may never have been there. honda makes motorcycles to last forever and considering jap restrictions on 400cc motorbikes thay could be pretty conservative with the airbox.

What are some mods for the air box?

Do you have any opinion on the TYGA 'race air box' that claims more volume?