Gas analyser

[xwhatsit]

Hello,

Trying to make my bike go properly. It looks like to properly pin down what's going on, I need to do a gas analysis test.

Does anybody have one of these? Is there a shop that will quickly do this check for me, and not charge me hundreds of dollars or so? My uncle reckons most garages would have one lying around.

I don't want to do a dyno run. I just want to check if it's running lean, and if so, how much by. Yes, I can do a plug chop, but it's not really very helpful. I also want to see where it's lean.

Thanks guys. I want to be able to ride my bloody bike. Don't want to spend two months on a bus again.

[Kickaha]

I don't want to do a dyno run. I just want to check if it's running lean, and if so, how much by.


But a dyno run will show you exactly where in the rev range it is lean

[The Stranger]

Hello,

Trying to make my bike go properly. It looks like to properly pin down what's going on, I need to do a gas analysis test.

Does anybody have one of these? Is there a shop that will quickly do this check for me, and not charge me hundreds of dollars or so? My uncle reckons most garages would have one lying around.

I don't want to do a dyno run. I just want to check if it's running lean, and if so, how much by. Yes, I can do a plug chop, but it's not really very helpful. I also want to see where it's lean.

Thanks guys. I want to be able to ride my bloody bike. Don't want to spend two months on a bus again.

What is happening, or not happening to make you think it may be lean?

Sometimes you can tell if a motor is running lean by opening the throttle a ways, wait a second or 2 then gently back off the throttle a little.
If it accelerates as the butterfly/s close and corrects the mixture it is lean.
Doubt it is very accurate, but it pointed me in the right direction with an outboard motor a few months back, the main jet of one carb was blocked.

[Mark Pav]

It is more likely to be lean at a combination of throttle opening and revs.Throttle opening the more relevant parameter on most occasions. Proper dyno run with gas readings the best idea. You have to load the engine to get accurate gas readings, that is whwt the dyno will do.

[PeeJay]

Hello,

Trying to make my bike go properly. It looks like to properly pin down what's going on, I need to do a gas analysis test.

Does anybody have one of these? Is there a shop that will quickly do this check for me, and not charge me hundreds of dollars or so? My uncle reckons most garages would have one lying around.

I don't want to do a dyno run. I just want to check if it's running lean, and if so, how much by. Yes, I can do a plug chop, but it's not really very helpful. I also want to see where it's lean.

Thanks guys. I want to be able to ride my bloody bike. Don't want to spend two months on a bus again.

check this guy out
www.triplezeecycles.co.nz

[Hoon]

The engine has to be under load. You can't just hook it up while its idling in the garage - all that will tell you is what needs to be done to get the ideal "idling in the garage" setting. Likewise with reving it on the stand. You need a Dyno.

Otherwise all you can do is make random changes, test ride, rinse and repeat until you strike it lucky.

[xwhatsit]

Here's a question while I've got a captive audience;

After swapping carbs and changing jets/needle position, it's running very well. Running cool, performing well as soon as I open the throttle, plenty of power. Fuel consumption has increased a wee bit, but that's to be expected.

However the thing, whilst idling well at first, once it gets hot from sitting still in traffic for a while starts to idle like complete shit. It'll just start missing and farking about at closed throttle or even slightly open throttle, until eventually (if I don't hold the revs up) it just dies. Then it's time to bump start from the traffic lights, fun and safe!

Fiddling with the pilot mixture setting didn't change anything (in fact it seemed to make no difference to anything, really), and putting a new sparking plug in improved things somewhat but it hasn't cured it.

Any thoughts?

[Kwaka14]

Try a timing check or valve clearance maybe

[xwhatsit]

Try a timing check or valve clearance maybe

I did both of those, timing is spot on (maybe half a degree retarded at idle), and valve clearances were a wee bit loose but are now spot on.

[Kwaka14]

Maybe how clean is the tank? is there condensation?

[xwhatsit]

There's a fuel filter on, no rust in the tank. I chucked some meths in there when these problems first turned up, didn't make a difference. Also with a full carb strip, even in the original (poorly performing carb) there was no gunk or water.

The thing is, is that it starts well enough from cold, idles perfectly, everything is fine -- until it sits in traffic for a while and gets hot and then the idle turns to shit. It only turns up when the engine is hot from no airflow.

[Kwaka14]

you could have a cracked head maybe I'm a bit stumped... might be worth getting that tested?

[xwhatsit]

you could have a cracked head maybe I'm a bit stumped... might be worth getting that tested?

Yeesh... don't even say the words! :sick:

Cracked heads are endemic to the breed, unfortunately. Replaced the original head because of that. Sure hope I haven't done it again (although with prolonged lean running it's more than possible).

Oddly enough I've heard several stories of people who have run these motors with cracked heads for tens of thousands of kilometres, running absolutely perfectly.

It has 175psi of compression, however; and that was with a properly hot and warmed up motor. It's like below xxx-degrees Celsius, it's fine, but once it goes over xxx-degrees Celsius a switch is flicked and idling turns to crap. It still seems to run fine under power, however, although small running issues affect idle much more dramatically of course.

[MaxB]

This is a longshot. I know you have considered this before but what about the CDI unit? They dont fail suddenly but gradually over time. It starts with it packing up in hot weather especially under load, like pulling away from the lights or high speed running. It may take months to crap out entirely and your bike would still run OK from cold (for a while).

Years ago I remember sorting through a wreckers box of used CDI units trying to find one that worked on a mates 250rs. Getting a good one was difficult because it was a common problem.

[xwhatsit]

Ah, interesting. I have a couple of boxes of spare bits; I'm sure there's a CDI in there.

Might be worth swapping over, cheers.