two schools of jetting a GS-> checking main's on plu

[fsrdh]

got the new K&N pod filter .
put 142.5 mains as the first ones(cobra exhaust). I want to test the plugs
to check if the bike's not lean when running mains .
Now this is where it get's tricky .
From all the articles I read there are 2 ways to  do it
first one depends on throttle opening ( IMHO correct one )
second one depends on RPMS

I cant find any road that I could run for 15 sec 3/4->WOT
as I redline way faster then that . I can get the bike to run
easily on 9K RPMS for a while but the throttle is only 1/3->1/2 open
so how to I check if I'm running lean on the mains ?
I have bigger jets too ( 145/147.5 )  but I want to do the plug check
before I start playing with the other ones .

[The Buddha]

Well you make the run on an open road with nearly no turns. I have often had to ride 30-40 miles before I got to that point... luckily In this stage of my jetting I was in Canada in winter and just ~2 miles from such a road. But anyway 3/4 - full throttle in 6th gear and 5 seconds at steady rpm should do. Yes you'd be doing 8-9K rpms, and doing near 100 mph, and yes hitting the kill with the throttle WFO and clutching to a stop will feel disconcerting but dont panic or pull over too fast into the shoulder or do some else stupid and wipe out.. and you'd be fine. Soon you'd be dreading the thought of handling the hot plug than the actual pull over part. Work gloves soaked in water in a ziplock baggie in your back pack/tool area come in handy. Wait a few min after pulling over... cos the motor needs to cool off a little. You dont want cold air entering a hot motor through the plug hole... that may cause stuff to warp. Soon you'd start worrying about that instead of the hot plug. Or do a dyno run with a O2 sensor at a shop.
Cool.
Srinath.

[JamesG]

Your carbs and plugs do not care how fast you are going or what gear you are in.  
1st gear from a stop WFO to 11K rpm for a few minutes is as good as 110mph in 6th. You are testing the carb's fuel ratio at a particular throttle opening, not how fast you can climb the tach & speedo. And they are easier to do on surface streets, at least until the neighbors call the cops on you...

Plug chops aren't a very precise way of checking jetting on 4 strokes. They are very subjective and require clean newish plugs.  Getting some time on a Dyno with an O2 sensor is much more effective.

[fsrdh]

Thats exactly what I'm talking about .
Two schools .

JamesG : I cant run the bike in first gear on full throttle for a few minutes as after few seconds I redline it . So what is the correct technique to do it .
the only way I can go full throttle and not redline to 12K RPMS is 5-6 gear
I can also keep the bike on any other gear and rev it steady to 10K RPMS
I just want to know how to make sure its not lean .

[The Buddha]

Precisely.... To make sure you not lean... Put in 150's and then run it. Of course Dyno+O2 sensor, or just O2 sensor in the pipe and ride it for a few weeks... That is just what I did...
Cool.
Srinath.

[miket]

JamesG : I cant run the bike in first gear on full throttle for a few minutes as after few seconds I redline it .

That's exactly why usually people suggest to do it in 5th ot 6th gear. You may able able to find a steep enough hill to do it in 2nd or 3rd.

That said, I could never read much from my plugs. It could be because I have never had my jetting way off. Usually I just go by "feel". Of course, like Srinath said, an A/F meter would be the best thing.

[70 Cam Guy]

Does it work to tune by temperature on these bikes?  There has to be an optimal temp range the bike likes to run at and I bet a/f ratio probably plays a large part of that on engines like ours.

[KevinC]

It doesn't take much of a hill to be able to hold the throttle wide open for 20 seconds on the GS. From 4 grand or so, it will take forever to get to redline in 6th with the throttle wide open.

There is not two schools. Holding an rpm doesn't do anything for tuning. You have to hold the throttle at the range you are testeing: wide open for mains, 1/2 to 3/4 for needles, etc.

If you have a proper plug socket, the hot plug is not an issue. Air in the plug hole isn't an issue. If cold air entering the combustion chamber is a problem, you better put a sock in your carbs, they do it several thousand times a minute.

The only temperature you can tune by is exhaust gas temperature. That works quite well, and is easy to tune for max power.

[fsrdh]

will try the 145 tomorrow If the bike runs better will do the 147.5 saturday
Also how much would it cost to get the bike on a Dyno without having the mechanics work on it it  , so I can just get the mixture printout  ??

[The Buddha]

It doesn't take much of a hill to be able to hold the throttle wide open for 20 seconds on the GS. From 4 grand or so, it will take forever to get to redline in 6th with the throttle wide open.

There is not two schools. Holding an rpm doesn't do anything for tuning. You have to hold the throttle at the range you are testeing: wide open for mains, 1/2 to 3/4 for needles, etc.

If you have a proper plug socket, the hot plug is not an issue. Air in the plug hole isn't an issue. If cold air entering the combustion chamber is a problem, you better put a sock in your carbs, they do it several thousand times a minute.

The only temperature you can tune by is exhaust gas temperature. That works quite well, and is easy to tune for max power.

Tuning by pyrometer - Exhaust temp is hard and un reliable especially on bikes with pipes out in the open.
No one said cold air is bad for the motor... when running. When its not running if you have a valve that has gotten hotter than usual, you dont want cold air entering and hitting the valve ... Ok well usually the plugs being pulled out wont hurt the motor...
Cool.
Srinath.

[KevinC]

I still don't understand Srinath - cold air hits the valves every intake stoke, lots of it, even cooler than ambient due to fuel evaporation.. The air exchange through a spark plug hole is trivial in comparison.

What does running have to do with it?

For that matter, if the engine stops with a valve open, which it generally does, the area open for "cold air" is far bigger than the spark plug hole.

That is all nonsense.

[fsrdh]

How much would it cost to get the bike on a Dyno without having the mechanics work on it it , so I can just get the mixture printout ??

[KevinC]

Oh, and almost every reciprocating aircraft engine in the world is tuned by EGT temperature repeatedly during flight. It works much better for tuning for power and fuel consumption than an O2 sensor.

The pipes out in the open has nothing to do with the EGT mid-pipe 150 mm from the exhaust valve.

Oh yeah, and EGT is the method Factory Pro uses to develop their jet kits, and most racers use to tune engines.

Dynos can be $25 a run, to about $100 hr.

[JamesG]

I think while Seshadri was playing Dr. Frankenstien with his dead shock the spring must have come off and hit him in the head. He hasn't been very coheirent lately.

:mrgreen:  

[werase643]

yes Srinath is talking out his ass AGAIN!!!!! :nana:

" Soon you'd be dreading the thought of handling the hot plug than the actual pull over part. Work gloves soaked in water in a ziplock baggie in your back pack/tool area come in handy. "

yeah....water is one of the BEST conductor for heat transfer....good way to steam your fingers from inside your gloves.....

[JamesG]

Be nice. Only one person at a time gets to pick on him.  

Besides, the plug thing was more of a suggestion...

[werase643]

I thought it was my turn

:mrgreen:

[The Buddha]

Oh, and almost every reciprocating aircraft engine in the world is tuned by EGT temperature repeatedly during flight. It works much better for tuning for power and fuel consumption than an O2 sensor.

The pipes out in the open has nothing to do with the EGT mid-pipe 150 mm from the exhaust valve.

Oh yeah, and EGT is the method Factory Pro uses to develop their jet kits, and most racers use to tune engines.

Dynos can be $25 a run, to about $100 hr.

OK on a GS the 150mm from exhaust valve is ~right about where the crossover is. It wont work due to a number of reasons...
Contamination from the cross over, road speed cooling off the pipes unevenly (hotter the day, hotter the pipe, more humid the day colder the pipe etc etc) If the pipe was straight through to the exhaust port it might work, or if it was shielded from direct wind blast it may work, It may work in a lab on a dyno cos they can shield it for anamolous wind, but in actual use conditions it wont. I also know that those big semi truck engines have a EGT. The shortest pyrometer I have seen is ~7inches long. The thing has to be fixed right in the center of the pipe to get the hottest part too. All cars use O2 sensors... all of them, most of them dont have pyrometers. Maybe its got something to do with the fact that its a gas engine... An O2 sensor analyses chemical composition of the exhaust gas, abd is read with a milli volt meter. Unless you have a hole in your exhaust pipe the exhaust gas wont change chemically and hence un affected by contamination from anywhere.
Ok so as intake charge enters and its cold... why do valves end up getting hot??? yes I know... in the combustion and exhaust cycle the temp goes up, and it drops a few hundred degrees in the intake cycle... The final temperature of the internals of a hot motor is still close to 400+ degrees. The outside air would be between 70-100 degrees... from 400 to that temp range is still cooling, and it can cool unevenly and warp. Exhaust pipe mouth is so far away... And people still plug them after a ride... as a precaution.
Cool.
Srinath.

[The Buddha]

yes Srinath is talking out his ass AGAIN!!!!! :nana:

" Soon you'd be dreading the thought of handling the hot plug than the actual pull over part. Work gloves soaked in water in a ziplock baggie in your back pack/tool area come in handy. "

yeah....water is one of the BEST conductor for heat transfer....good way to steam your fingers from inside your gloves.....

No you wont steam your hands. Not by holding the plugs... maybe if you held the exhaust pipes with the motor running. Yes it will get warm maybe... but the plug dont have enough heat in it to even give you any discomfort through water soaked gloves. Well other than the feeling of wearing wet leather gloves...
Cool.
Srinath.

[KevinC]

The carb throat is very close to the valves, and I have never seen anyone plug an exhaust pipe.

I cxan't remember what the stock GS exhaust system looks like, but the Yosh and Hindle don't have a joint or cross-over anywhere near 150 mm from the exhaust valve. I've been running with EGT sensors there, in the middle of the pipe, for a year. The ambient temperature, wind, speed of the bike, etc. make no difference to the reading. Load and throttle opening do. Jetting does. I suspect you've never tried it.

Most race cars run withan EGT, as well as every kart I've seen. It's by far the best way to monitor combustion.

O2 sensors are the best way to measure for emmisions, which is what the car manufacturers are worried about, with the EPA standards they must meet. It is not the best way to monitor for best power and fuel economy.

Using a ten year old American O2 sensor  that you olnly have a vague idea how it was calibrated when new seems pretty flaky to me.