One for the 250cc folk

[generatorshovel]

WOW ! Thank you kindly for sharing your experience & wisdom Robert. 

[Peter Jack]

Sorry for the hijack a couple of posts back Tiny. My reply was to WobblyW about the wind tunnel and didn't pertain to your problem. If you had me working on that you'd likely be buying pistons by the bushel basket. 

Pete

[generatorshovel]

In a few years when I retire I am going to drive ti A2 wind tunnel with the bike and rent a space at the local KOA for several days.  The bike will go into the tunnel, I will make some mods, and it will go back in until I get the aero sorted.  The I drive back home.  Maybe you could do this at the dyno shop?

Unfortunately Bo, our Prime minister keeps shifting the retirement goal posts, now the male retirement age in Oz is 67, or if you were born after the baby boom years, 70 .
This might be ok for someone like a politician, who has never don't a days hard physical day's work in their life, but the average working man has to abuse his body to earn play money, to do things like LSR,,,,,,
I still have 6 and a bit years to go, so that option is out.

Sorry for the hijack a couple of posts back Tiny. My reply was to WobblyW about the wind tunnel and didn't pertain to your problem. If you had me working on that you'd likely be buying pistons by the bushel basket.  

Pete

I realized this Pete, no problems with me


When I melted the piston in '13, I had gravity feed fuel (bad mistake) dirty plugs (which cleared)and a sort of lean midrange, and very fat main jetting, watch this video below, I think when the engine cleared just before hitting 5th gear, the engine was starting to starve for fuel

http://youtu.be/z_L8DsJis2o

This next pic os of the F1-11 dash during the last test run, the #4 egt is unreliable (poor 12v supply I cant find the reason for) although it is the hottest cylinder, 1 thru 3 are a close indication of the egt average temps



When I was planning this rebuild, I decided, after believing the manufactures claim their gauges are suitable for "all" fuels, including alcohol, which should helped me set up the carb, but in fact, it thru me right off target (live & learn)

Thanks again for everyone's input

[wobblywalrus]

Tiny, those combustion chambers are real small and the plug is in the center of them.  The flame only travels a very short distance in comparison to the much larger chambers we are used to.  It may be, because of this, that the little Honda needs a lot less spark advance than we think it should have. 

[TheBaron]

Tiny,,, I have another possibility of the low EGT on the #4 cylinder....

When a cylinder is detonating, the EGT reading reads LOWER !!!

Why ? Because the amount of heat going into the exhaust is reduced as the heating of the combustion chamber and piston increases.
(there is only so much available after all). Detonation produces shock waves that destroy the insulating boundary layer of gas next to the parts so the heating of the parts increases greatly.

I'd test all the EGT probes and gauges with a common heat source to see what is what, but if #4 holed a piston I'd say that that EGT was reading correctly at that time...

Robert

[RansomT]

Do you have enough slack in the cable to switch #3 and #4 EGT sensors?   You can then see if it is a voltage issue.

[generatorshovel]

Tiny,,, I have another possibility of the low EGT on the #4 cylinder....

When a cylinder is detonating, the EGT reading reads LOWER !!!

Why ? Because the amount of heat going into the exhaust is reduced as the heating of the combustion chamber and piston increases.
(there is only so much available after all). Detonation produces shock waves that destroy the insulating boundary layer of gas next to the parts so the heating of the parts increases greatly.

I'd test all the EGT probes and gauges with a common heat source to see what is what, but if #4 holed a piston I'd say that that EGT was reading correctly at that time...

Robert

The swapping of leads was done with #1 & #2 a while back, all thermocouples were tested in the same boiling water pot, the chinese seem to have a problem with accuracy,,,,,,,

I don't take the EGT's as gospel, rather an indication changes have worked with jetting

Sometimes when I flick the ign s/w on, there is no reading with #4 until I tap the gauge  
Ambient temps before engine start vary (sometimes #4 is also feint)

Do you have enough slack in the cable to switch #3 and #4 EGT sensors?   You can then see if it is a voltage issue.

Yes

[generatorshovel]

I'd test all the EGT probes and gauges with a common heat source to see what is what, but if #4 holed a piston I'd say that that EGT was reading correctly at that time...

Robert

There were no EGT figures available the year I melted the piston Robert, I had the idea they would slow me down if I looked at them (as happened in 2006 with my Postie bike,,1350degrees 1 mile before I reached the 1st timer), I backed off a bit , got the temp down to 1200 and got a time, fully how 3/4 throttle went as quick as WOT did,,lol

[wobblywalrus]

A knocklight sensor is attached to my cylinder block.  The light is right near the tachometer and it is on the dash just under where I look when I am going down the track.  It flickers red when there is any detonation.  That red light gets my attention quick.  It is easy to see.  It has paid for itself a hundred times by telling me if my fuel choice and advance curve are not compatible.

The sensor performance is simply related to piston diameter.  A racer on this site verified my sensor was correct for my piston diameter.  You need to do this 'cause of the little guys that are in your bike.  You will need a different sensor than the one supplied with the light.  It is for bigger pistons.  PM me if you want details.

Do not get discouraged.  Racers from all over the world are wanting you to succeed.     

[generatorshovel]

PM sent Bo

[wobblywalrus]

Tiny, here is the info on the knock light I use.  Some of these lights are pretty complicated with all sorts of adjustments and other mental stuff.  I wanted something real simple that I do not need to think about.  The light is the self calibrating one on www.knocklight.com/Knock-Light-Store.html

The little bracket is removed from the light and this water resistant case was made from copper water line tubing and fittings.  Normally it is tied to the fairing dash with zip ties.  Now it is zip tied to the handlebar.  We look at it during the dyno work and the fairing is not on the bike when this is done.

The light glows red during detonation, the occasional chain rattle, missed shifts, etc.  The mind quickly learns to filter all of this out and to focus on detonation.

The sensor is shown.  These are sensitive to different input frequencies and their selection is based on piston diameter and the desired harmonic.  It is best to discuss this with the manufacturer.  The sensor I use for pistons of almost 100mm dia would be deaf to the rattle of the little ones in the 250.

Hopefully this is the info you need. 

[wobblywalrus]

Just read the new knock light topic.  The sensor is attached to the side of the cylinders by a stud.  It is real close to the source of detonation shock waves.  Maybe that is why the light works well.

[generatorshovel]

Thanks for sharing Bo

[generatorshovel]

I think I'm ready for 2015,, managed 121 with under control EGT's, plugs look ok, a tad darker on the fire ring with #680 mains, compared to #640 mains, not textbook discolouration, but "safe"
http://youtu.be/oNbWwK05phQ
It will be interesting to see how far it'll wind out in 6th ?

[wobblywalrus]

That looks like Burt Munro's test road in Nevada according to the movie.  The bike sounds good.