hi
im looking for advice on jetting for these pipes
from anybody who has had experience with them
the bike is otherwise fully stock standard
thanks
the two stroke terrorist
hi
im looking for advice on jetting for these pipes
from anybody who has had experience with them
the bike is otherwise fully stock standard
thanks
the two stroke terrorist
You could try a Gunson's Colourtune, it is a replacement sparkplug with a transparrent quartz window (costing about 14 pounds). It allows you to actually see the colour of combustion (yellow=rich, white=lean, blue=okay). This should be a lot more accurate than a plug-chop.
The jetting suggested by Jolly Moto in their instruction sheet is very close. They suggest changing the jets to one size leaner on each carburator or 260 and 270 left to right.
thanks for the replies
both helpful
id be interested in getting the spark plugs but im in sydney and havent heard of them out here
rsv 250 sounds like you have had experience with the pipes
if so how did you find them
Gunson sell direct from:
www.gunson.co.uk
Select gas analysis/mixture control from the menu, I have the standard one, but I notice they now have a high-temp one for motorcycle engines... I have found the normal one to be okay though and its a bit cheaper.
Hi Keean, how do these things work? Do you just screw em in instead of the plug and go for a ride and then read the glass?
I take it that once your happy with the mix you put your normal plug back in. How accurate are they? Do you get different readings when you change by one jet size?
Your reply will be much appreciated. Thanks
It is simply a spark plug with a quartz window, trough which you can view the actual combustion in the chamber as it happens. You shouldn't really ride with it in - what you do is go for a ride with normal plugs until the engine is at full running temp. You then stop and swap in the colourtune plug and restart the engine. As for accuracy thay are more accurate than a plug-chop but less accurate than an exhaust gas analyzer... I am not sure whether a single size change of jet will show up... But jetting set wioth a colourtune has been found to be spot on under accelleration using an exhaust-gas-analyzer, although a bit lean under idle, and deceleration... although maybe they didn't do all the tests in the colourtune leaflet!
Interesting. What size does the Priller need? 14?
Ted
I am not sure of the size, I just bought the standard kit (no adapters) and it fits fine...
Keean
How can these be more accurate than a plug chop but less accurate than an exhaust gas analysor? How many Gp teams use this colourtune or an exhaust gas analysor on their GP250 bikes? You can not get any more accurate reading of what an engine is doing than by doing a plug chop and removing the heads.
If you should not really ride the bike with this colourtune thing in how is it going to tell you how the bike is running under load?
I think you'll find GP bikes run dataloggers with detonation sensors/temperature sensors/rpm data/trottle position etc, allowing (when the data is downloaded into a computer) very accurate analysys of the performance under real race conditions...
An EGA will give you an exact percentage of oxygen/CO/CO2 in the exhaust, so you know exactly how rich or lean it is... When you do a plug chop you are viewing the after evidence ... the remains of several thousand explosions... With colourtune you see the actual colour of the flame second by second... (you are actually seeing the flame inside the engine - rather than looking at the soot left behind) You can run it under load using a dyno or other rolling road - its just not to be kept at high RPM for more than a couple of minutes. Anyway i'm not trying to sell these things!
You make statement (plug chops are better) yet give no justification for this - so its just an opinion, which is fine.
Yeah but like Stu says you cant look down at the plug when your riding your bike at 100mph, and think ahh i think its running a bit weak!
They cant be more accurate than a plug chop, because the motor isnt under any load when your revvin it in neutral, so wont give an accurate reading.
Ok My justification is you are running the bike exactly as it is without changing anything on it. The reading you get from the plugs and heads is exactly as it is run on the track. Even running a bike on a dyno seriously changes what happens as the revs change quicker, the loading is not as much as on the track. What I need as an engine builder and racer is to know what is happening at the time when i want the engine to perform best which is when it is being caned on the road or the track. If anything is changed when you are trying to set it up it will not be spot on.
If you fit a Colourtune plug you have changed a critical item of the engine. You don't get the colourtune in different heat ranges and resistances like you do with plugs so you are never going to duplicate the actual running of the engine. I am not knocking the product, just saying what i think.
I know about datalogging det counters and such as I run an 85hp RS250 Honda with a BPS programable ignition with datalogging, det counter etc. I also do plug chops to set the bike up as it is the best way I have found. But then again that is just my opinion.
Okay, I agree that changing anything from actual running conditions will affect the results. I think what we have here is a differing definition of accuracy. When I was talking about accuracy I was refering to numerical accuracy (ie how small a change in mixture can be detected by each method - and I still stick to this - A colourtune will show a cylinder to be rich or lean when a plug chop will show it to be alright, whereas a EGA can detect parts per million, and completely blows the other methods out of the water...
Also different jets in the carb affect the engine at different RPMs and different throttle openings - how do you know which jet is rich/lean with a plug chop.
Here is an example - you have a lean power jet and a rich main jet... you take the bike out and do a couple of laps - what will your cylinder head look like?
I would also like to point out that the heat range of a plug does not affect engine power output... A cold plug conducts heat away from the ignition electrode better - to prevent the tip of the plug melting in high-performance engines... A hot plug conducts heat less well, which keeps the tip hotter so that any oil deposits burn off... that is all... so if your plugs foul run a hotter one, it has nothing at all to do with combustion characteristics in the engine, apart from of course a hot plug makes detonation more likely as there the compressed gasses will have a hot bit of metal in contact with them... So in summary fouled plugs = run hotter, detonation = run colder, so I would assume as long as the colourtune is not too hot it will be fine, as you're not really running it for long enough to foul, and you clean it with acetone between each run anyway.
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