EC300 losing power + rattle
 

Ok so I've had this problem appear 2 rides ago, I'm forming a theory but won't get to check it for a while. On that ride I was putting the bike under load going up a hill, but certainly had done bigger hills that this, not intense, in fact earlier I had done a long steep uphill with no drama.

Anyways the bike starts making a rattle & loosing power to the point I decide to stop & restart. I nurse the bike back to the pits & decide what to do. But it is now running fine. I start off for another loop & thrash it just in case if shows an error I can shortcut out of the loop. Runs fantastic, pulls good wheelies. Then stutters coming out of a shallow river crossing.

So back home pull it down & PV is smoothly turning, piston is peachy but very worn, figured that anyway, but no pick ups, no deto marks. Crank seems fine with no movement I can detect wobbling the crank ends or the rod, no discolouring. As you?d expect an 07 to be really.

New piston, fire it back together, adjust the PV so there is no slop (not really much before) in the governor arm.

Next ride yesterday.
All went well, less rattle, ran it in, all good, bike peters out on a hill again with accompanying rattle. No power almost to a stop. Give it a few seconds still running & it comes right & returns to full power. Do rest of 25k loop with no problem.

By now I'm thinking carb float sticking. But makes a rattle that doesn't make me think its running out of gas, but maybe that is deto from lean mixture on a big cylinder under load.

Don't fancy taking carb apart in a field so do a loop on the Trials bike I brought along (its ok it's a GG). Go out & do another loop on the EC300. Up a hill & it looses power again & actually stop, then blipping it trying to keep it running & it stops. Then 10 sec restart it & it clears out & runs fine. Although a few times under load I notice a tendency to seem like it is teetering on the edge. I also notice a few knocks like deto.

So clearly I will pull the carb & check the float valve & check float height. But seems queer as the carb hasn't been apart for several rides. No mechanical issues I can see, even the reeds looked nice from the crank case (top end removed) with a torch.

Water would stop it & make it backfire I would have thought.

Any other ideas?


OK further thoughts. The pipe is a euro road catalytic pipe that was cut open & the cat removed. For some strange reason it rattles more than the other pipe (which is a bit squished). Small poss that something is dislodged & blocking the pipe somewhere. Had this pipe on for about 3-4 rides before seeing an issue.

Can't see the ign going into some queer mode, but possible I guess (happens on rain & full power mode).

So open to the panel:

Ideas :) ..I'm an ideas man!!

I noticed when my powervalve stuck open the engine sounded rattley like it was about to blow up. The bike was so soft on power that it could hardly pull me around off the pipe, and the engine sounded so ill that I didn't dare rev it hard enough to put it on the pipe. Limped it home.

When you checked the powervalve actuation was it with the cylinder off? Did you rotate the powervalve through a frull 360 degrees forward and back? I found mine would sometimes hook up on the return. Other times not. A good clean of the entire assembly fixed it up.

Also an easy check if you think its running lean on you, cut the engine when it plays up under load and pull the plug. It'll tell you how its feeling. You could possibly use this to check the location of the PV as well if you popped the LHS off, or pipe/RHS (both). Depends where you are when it happens next.

If you suspect water in the fuel it will be evident in the carb drain bolt as the lowest part of the system.

Hmmm
 

Have had a similar issue with my 2010 300. I have had a couple occurrences where I get a rattle/change in pitch and slight decrease in power, maybe. 10% decrease. This lasts for a few seconds and goes away. It seems to happen when i hit a large rock or root-some on here associated this with the pipe taking a hit and loosing its seal with the head.

Hmmm

I'm talking about an 80% change in power. As I said it actually stopped at one point, it was very dead feeling trying to blip it.

I had the barrel off when I changed the piston & I decided not to pull the PV as it seemed so smooth through operation. The governor seemed to move ok but can only push a little due to spring. Its bathed in oil so shouldn't be a problem, but can't rule that out, I started to take it apart to check the balls & didn't go any further when it seemed ok.

Interesting that you (Jakobi) had similar symptoms, but maybe not quite. I'll keep it in mind for sure.

I don't think the plug would change that quickly, remember that it runs great most of the time & then Nunnnggg rattle rattle.

Only takes a few secs to change a plug up, especially if its extreme enough to cut the engine out :cool:

My symptoms never came and went though. When mine stuck it stock wide open until I removed the RHS power valve. When I went to crack the lock nut on the actuator arm the valve returned to normal. I unclipped the arm and ran the valve between its stops. Fine smooth action hooked it up and it stuck at wide open again. It wasn't until I removed the stops and ran the actuator plate through its full motion in forward and reverse that I noticed some minor binding on reverse. It wouldn't happen at the same time or the place. Ended up being some carbon deposits.

I would say that I would have lost 80% power easily. Scared the shit out of me as I'd just been making jetting changes before it happened. It honestly felt and sounded like the rings had fallen off the piston. Would not idle well either.

so what ditd you do to repair it, just clean?

http://www.gasgasons.com/index.php?s...c&staticID=133

Above shows step by step with pics. Pulled the assembly. Cleaned the carbon off everything. Repacked the bearings with grease after checking they were running smooth. Re assembled. No issues since.

Power loss, rattle, knock equals lean to me. The fact that it happens on hills and after a water crossing is suspect. How are your carb vent lines routed? Are they clear? All down is bad. Split them and route the pair from the vertical fittings up high as has been discussed here many times. Also check/clean carb as it can suck dirty water if all lines are routed down.

Don't overlook the gas cap, cost me a race once. The pin holes in the rubber insert/gasket can swell shut and block venting. Cut this middle section out(or replace it with a homemade ring gasket), enlarge the holes in the plastic retainer for the check ball, glue this back on and make sure the ball is free.

Try the simple things first, PVs and pistons don't care about hills.


Jakobi,

The PV bearings are best just cleaned well or replaced (cheap) and lubed with a little two stroke oil. Spooge oil keeps them alive in use. If you run a good high flash point oil they should never be fouled with hard deposits.

Thanks for the info Glenn,

I had given the bearings a good clean first and considered replacing but there was no play or binding in the bearing itself. Mine was some carbon on one of the powervalve rollers (either side of the main flap). I had been using GGs recommended GRO at 50:1 as per requiresments of GG aus in order to retain my warranty. Since that is now up I am trying Amsoil Dominator. Have only ran half a tank through it so hard to comment yet.

Good thinking re the gas cap/vents. I don't know how many times something simple like this has stopped a bike from running.

Does the engine get a lean surge like its running out of gas before it dies?

Thanks guys I'm getting some good alternative info here, hadn't thought about the gas cap & yet have had this problem on roadrace bikes.

Carb vents. . . erm, heck you know I can't remember. I definitely went through the 200 & did them up & out of the way/airbox. Can't remember if I did the 300 fully.

Re the engine lean surge, well, it would be masked, if you are going up a hill you are under load so you won't get a surge, just a big loss of power then the gas would get so low that it would hardly run. That is what made me think carb, but tank venting is an interesting alternative & why these forums are a good sounding board.