MH80
11.05.2021 6:39:57
Re: Symptom of reed valve failure?
See full version: Symptom of reed valve failure
Re: Symptom of reed valve failure?
A broken/ leaking reed in a multiple cylinder engine will cause that cylinder[with the bad reed] to act lazy. depending on the size of the leak, the engine could run fine at WOT, but will always be lazy at idle/part throttle. a broken reed allows the intake charge being compressed in the crankcase to bleed away. so that particular cylinder will act lean. an extra shot of fuel down the bad cylinder will generally make it fire briefly. an experienced tech can usually pick up a bad reed just by listening at the carbs when the motors idling. they make a distinctive sound. an engine with a bad reed will have the same compression in the cylinder as a good one would, unless the broken off piece caught in the piston/rings and damaged them. more
Re: Symptom of reed valve failure? here
Low compression is one symptom.<br />Spitting fuel from the carb,or air pressure fealt when hand-choking it.
If the top end is worn out, or there's a gasket that's not sealing (ie: blown head gasket, leaking base gasket) the motor could be low on compression, and low compression certainly will make an engine hard to start, if you can get it running at all. here
As part of your preliminary diagnosis, you'll want to ensure that the electrical connector at the fuel injector(s) are undamaged, secure and have 12V of continuous power to one side of the plug and a pulsing ground to the other, anytime the engine is being cranked as the injector(s) are frequently powered by a constant power supply while the ECM sends a ground signal to the non powered wire to control when and for how long the injector is "fired" / enabled / turned on which is controlled by the ECM and is referred to as injector pulse width. more
The safest bet for getting the most longevity out of any engine is to keep an eye on the air filter and check out the article on: Keeping your air filter and intake clean as if the motor depends upon it.
If the motorcycle does not have a kick start backup, it may be possible to push start the motorcycle. [links]
So pressing the electric start does nothing at all or little more than click but you're sure you've got power at the battery, or even better, the headlight or taillight brightly illuminates when you turn the bike on, we'll be able to get a rough idea as to the battery's amperage capabilities, as well as the integrity of the electrical system (ie: tightness of connections) as all too often electric start bikes don't start due to loose or corroded connections so we'll be looking into this first. here
Right after re-assembly it started right up 3 rd kick.
Low end and mid range power good. Top end blubbers and 4 strokes.
Rode sunday and it ran good as long a did not go over a little over 1/2 to 3/4 throttle. Shut bike down after riding for an hour to push my granson up a hill. Went to start the bike and it took at least 20 kicks without a pop then it started all of the sudden.
Any input would be appreciated
It is strange that I can kick and kick then all of the sudden it will start. Can the bad reeds cause it not to hold idle. more
Can bad reed cause an engine to fall flat and 4 stroke on the top end ? I am experiencing real hard starting and the bike will not run on the top end. I also noticed what sounds like air coming out the back end of the carb when running.
The top end was just redone.
All new gaskets installed and torqued to spec
Compression test was 150 psi
Carb gone through all passages cleaned
New air filter
New crank seals both sides
No cracks or leaks on manifold
Exhaust pipe sealed with high temp silicone
The bike is a 1981 YZ465 Yamaha [links]
I have a Boyeson reed block in my 95 KDX200 and have gone though several sets of carbon fibre reeds since i got it. Like joe said it might be harder to start. but the biggest giveaway is a bad idle and power loss at low revs/bogging down depending on how bad they are. If your reeds are fine try cleaning out the pilot jet.
I am dealing with an issue with my KDX that I believe is a reed valve issue, have a new set ordered which will be here on Thursday so that I can pull the existing, evaluate them, and then reinstall the new ones.
I've searched this site for information/symptoms about suspect reed valves, but am amazed that there aren't very many conversations about them. more
If you've had experience diagnosing reed valve issues and can share them here, that would be great. It would certainly help me out, and also others that come here for support.
I couldnt work out why I was using so many sets of reeds it was annoying me because they cost me over $100 NZ dollars ($65-70 USD) each time. I haven't gone through any for over 50 hours now and I'm pretty sure its from riding it pinned/flat out (possibly only in top gear) for to long at the river and beach.
[links]