Reed petal chipped

[Jakobi]

Hi everyone,

Looking for a quick reply if possible. Today I was riding around. Stopped for a moment and then when I kicked the bike back to life it sounded very strange. I immediately killed it and wondered what had just happened. Kicked it again and it fired up but sounded very very strange. Kind of dull, like the choke is on but it wasn't. It wasn't smoking much from the pipe and the exhaust/piston sound was very notable. It almost sounded like the piston was slapping/knocking/exhaust was cracked. There was still pleanty of compression under foot but running the bike was way way down on power and didn't sound healthy. I limped it back home and pulled the spark plug, exhaust, carb and reeds. The plug looked ok. The exhaust looked pretty normal. Piston and jug showed nothing out of the ordinary. There appeared to be fuel residue pretty heavily left in the carb and the air boot. One reed petal has chipped the whole corner off.

I'll post a pic soon, but in your opinion would this create the kind of effect I experienced? If I get a new set of reeds and put them in, set jetting back to stock and fire it up should it be okay? Or am I looking at pulling the head/jug/digging deeper.

Another new experience in the world of bikes!

 

[Jakobi]

Pictures..

 

[thumperrider1]

Providing the top end looks ok, I'd swap the reeds out and then fire it up and see if it sounds any better.

 

[boyscout]

Jakobi,
I recently had that exact experience myself, last set of reeds only lasted 5 hours. Replace the reeds, put it back together, and go back to your favorite way to spend time-- jetting.

Ps. the breaks in my reed pedals were much larger than yours. Ran fine down low but could not rev.

 

[GMP]

Thats not that big of a break considering the symptoms you describe. Actually the reeds do more at lower RPM and will affect that more than high RPM. Usually feels like bad (rich) low range jetting. Could you have a PV problem that is being masked by the chipped reed?

 

[Jakobi]

Thats what I thought too Glen,

The symtpoms and the way the engine sounded was alot worse than I would have expected from a worn reed. Come to think of it now, I think the powervalve may have been stuck in the open position when I peeked in the exhaust port. I did rattle it with my finger but only checked for the usual side to side play which there is a little bit of. I'll see if I can source some replacement reeds today, and then go home and pull the RHS powervalve cover to see what position thats in.

What does a shot big end bearing sound like and what would the symptoms be? This was my worst fear when I kicked it and heard the sound. Very rattley and very under powered. Might be worth while pulling the stator cover and checking for play in there aswell.

This is all the day before a ride! Looks like I might be riding team yamaha this weekend.

Really the feeling of a very weak and rattly bottom end could very well be the powervalve stuck open. I didn't rev it hard enough to see if it would clear up in the top end. Also would you suggest pulling the head to inspect the piston top and jug? or just start with the PV?

Thanks, Jake

 

[Neil E.]

Unless you drowned it in a creek, I doubt your big/small end bearings would fail that quickly. Stick in the new reeds, start it up and see if the power valve moves OK as you rev it. You can see the PV shaft through the left side cover if you want to avoid removing the pipe. The shaft should turn when you rev the engine.

 

[Jakobi]

I've got the pipe off now so I will remove the RH cover and make sure the actuator plate is where its meant to be. I may disconnect it and make sure the powervalve smoothly runs through its range of motion aswell.

While on the topic, has anyone else noticed in my picture that there is a restrictor inside the reed cage? What is this doing there? I have read posts about removing the spacer which I always assumed was the aluminium block between the reed cage and the carb. I wonder if this is the reason my bikes continually been jetted leaner than most others. I'll post a pic this evening. Disregard - identified the intake hole is the same size as that of the connector plate for the carb.

Could someone also shed some light on how the petals are actually connected to the block. Looks like they just slide in.

Update The powervalve was indeed stuck open both in the exh port and at the actuator plate. I went to undo the bolt holding the arm on and the slight force on the plate was enough to release the bind and the whole thing cleanly swung back around under its own tension to the closed position. I removed the arm and did I few rotations of the powervalve to confirm no binding. Nice smooth action through there aswell.

Will reassemble and start to see if the engine sounds better. Would any of you go for a ride on worn reeds or is it a gamble that more damage will occur? Probably best just taking the 250F until the new ones arrive!

 

[twowheels]

You could ride it just to verify that it will pull a load, but before I headed out on a long ride I might investigate why the PV bound up. Was it the actuator plate or arm? Did you over-rotate the drum? Some crazy rich jetting (hah!) left enough spooge to gum things up?

 

[Jakobi]

Hahah! The bike was a bit hard to start. I won't risk sucking a petal on tomorrows ride.

The powervalve worked properly while warming the bike up. Once warm I wicked it up and when the valve opened it stuck at the open position. This time I managed to removed the bolt fo rthe actuator arm without the plate returning. The arm then fell back into its resting postion under its on tension. I think its fair to say the actuator is working as it should.

However! The problem appears to be with the rhs powervalve bearing. Its very strange. In forward action its smooth and silky and rolls right around but in reverse it sometimes hangs up and I need to go forward and then quickly flick it and it'll roll back past where it hung. The LHS bolt turns for days on end and also helps release the right if its jamming. Based on this I don't think its the valve itself thats hanging anywhere and something to do with the RHS bearing. There is no notable play in it, but the small part that the actuator plate mounts on does have some in and out movement and maybe a little play. I wonder if its slightly off center and loading the bearing? Ideas?

Researching how to pull the bearing now. http://www.gasgasrider.org/pv_disassembly_mattr.pdf
Looking at diagram I'm betting part 31 is gummed up slightly.

 

[Jakobi]

And the last spastic question

Sorry to be a pain. How many posts can I make in one day??

I've pulled the PV assembly apart and cleaned it all up. I have left the actual flapper in there as I cbf removing the exh spigot to pop it out. I tried with it on and the piston at bdc but no go. There doesn't appear to be alot of build up on it.

Just wanted to confirm when re-assembling parts 31/32 PV Assy, where should the cut outs be on them when I put them back in. Are they in relation to the ports, the flapper, or both? Whats the best way to do this while the jugs still on the bike?

Thanks again.

 

[Rabbitist]

with the power valve sticking open i just wonder if gas gas are still sticking single sided sealed bearings in the valve assembly.. it only takes a little bit of shit to get in there and it can stick it open or any position.. i was told they are single sided bearings to let un-burnt oil lubricate them but if you use a good quality double sealed bearing like a fag bearing might stop it from sticking and doesnt need aditional lube. just a possibility..
luke

 

[Rabbitist]

i think 31 and 32 should be closed when the arm is down and the cutouts should open the port and flapper when the arm is raised

 

[Jakobi]

Both my bearings are sealed both sides. The more I look at the assembly I'm led to believe it will only go back together the right way. The main shaft is off center. The main flapper can be out of time by 180 degrees but I've got that one sorted.

 

[Rabbitist]

I think you could be right

 

[Jakobi]

Reeds

So back on topic. I'm about to replace the reed petals and have the cage broken down ready to remove the old and install the new. Looking at the petals currently in there they are in very good condition with exception to the one that cracked a corner off. Would you replace them all and keep the old ones as spares? Or simply replace the damaged one?

 

[PEB]

Replace them both. Unless you like the wrestling match of getting the carb boot back on, in which case replace one now and the other in a couple months.

 

[Jakobi]

Replaced them all while I had them out. I have saved the other 3 petals which are in A1 condition as spares.

Strangely enough you speak about wrestling with the carb boot. I haven't had any real issues at all with this. Little bit of finess needed but not too bad. In comparison prying the retainers for the inner reed petals out of the cage.. @&*^@!@^*)@)!*@&# .. I see why they send new ones with the new reed petals.

 

[n_green]

Old thread revival

No poin in starting a new thread, same thing just happened to my '11 300 reed petal although I didn't notice any change or loss of power just pulled the cage out for a look. This is the only petal that's damaged:

I blame this for the damage:

Obviously I'm replacing the reed petals. I'm concerned though that the new petals will continue to be damaged by the rough edges of the intake? Not keen on attempting to dremel them smooth and fill the crank with metal filings either.

Apparently the new vforce4 reed cage has stoppers that prevent the petals opening so far so this sounds appealing. I'm struggling to find the part # for the current vforce3 cage. Anyone know if it shares the cage with another bike or what the vforce part # is either vforce3 or vforce4?

Cheers

 

[n_green]

Mototassinari website says vforce4 only for KTM at the moment. Bugger. Looks like I'll be replacing the petals on existing cage.