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Yamaha 450 backfires flame & no idle.

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Serf27
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PostPosted: 04:35 - 28 Sep 2017    Post subject: Yamaha 450 backfires flame & no idle. Reply with quote

Hi again everyone!

2013 YFZ 450, not exactly a 2 wheel bike, but hopefully I can get some help on it please, it's driving me crazy.

Short story,
Stock jetting from factory is 152.5 Main jet, 47.5 pilot, 55 power jet.

Mods, K&N filter full pro circuit t4 exhaust.
Re-jet to, 162.5 main jet, 50 pilot jet, power jet stayed the same(55)

Sometimes it will idle, and if I slowly accelerate, it will take off and run fine till I stop. In neutral, it used to rev up ok. Other times, it will just bog and go about 5 miles an hour if I punch it or even if I slowly accelerate, which it is constantly doing now, back fires and shoots flames.
Now it won't idle, and if I get it to idle, and rev it in neutral, it just bogs and rarely revs up. Spits fuel into the intake side of the carb and gets fuel into filter air duct.

Any ideas?


Long story.
I got the quad and it didn't idle, and ran ok, same bogging at wide open throttle, had to slowly accelerate to get full power.
Cleaned the carb, cleaned the filter, put A/F screw 2.5 turns out, upped main jet to 162.5, pilot jet at 47.5 and would idle, if I slowly accelerated, it would run fine. When slowing down around corners, if it would bog, I would hold the clutch in, rev up the engine and release the clutch and it would take off, still shot flames.

Nearby shop said the diaphragm spring was either to weak or too strong, tried weaker and stronger spring, seemed to make it worse either way, put stock spring back in, now it wont even idle and won't ride like it did the other day.

I put stock main jet in, no difference, still rarely revs up in neutral.
The only difference from the other day when it ran alright, (still had to slowly accelerate or rev up with clutch engaged and release clutch) is I changed the pilot jet to a 50.

But today, it was running okay, would take off at a decent speed, and idle. Took it to the trails, and it just stopped idling or moving.

The shop is telling me to get the older style carb for it. I plan to get it, but i just want the bike running good till I get the older stayle carb.

Any ideas please?? Really want to take this thing out night riding tommorow.

Thank you in advance.
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 08:55 - 28 Sep 2017    Post subject: Reply with quote

Carb settings don't suddenly alter themselves so if it was running properly before, fucking with the jetting/screws/springs in the carb is going to make no difference. Yes if there was dirt in the carb but this would have been fixed first attempt. Incorrect jetting wouldn't cause intermittant problems, it would be consistant.

90% of carburettion problems are electrical. People mess with carbs because they don'tunderstand electrics.

From your description of what's happening, I genuinely wonder if it's spun the flywheel.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Serf27
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PostPosted: 19:40 - 28 Sep 2017    Post subject: Reply with quote

Thanks for the reply.

I agree that carb issues would be consistent.

The only electrical part on the carb is the TPS sensor, it runs the same way with the sensor connected or not.

Is there anyway to check if the flywheel has spun?

I've probably rode the bike 1 good hour since I've got it.
It didn't run right, but was good enough to get through that ride, now this. Rolling Eyes
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 20:38 - 28 Sep 2017    Post subject: Reply with quote

Serf27 wrote:

Is there anyway to check if the flywheel has spun?


Yes, you'd take the cover off and have a look at it. You might even need to undo it and pull it off to inspect the woodfoffe key for damage.

In a less invasive manner, you should be able to check your static timing is correct using marks on the flywheel.

The reason I mention it is that some of your symptoms sound like they are ignition timing related and the only way ignition timing will go screwey on a modern engine are if the pickup coil is loose/damaged or the flywheel is moving on its shaft
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Serf27
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PostPosted: 04:09 - 29 Sep 2017    Post subject: Reply with quote

Thanks again, I will try to pop the cover off and see how the flywheel looks and if the woodruff key is missing.
I will also check the timing.

Looks like the flywheel is submerged in oil on this bike. The right side houses the clutch, and I am sure the left side houses the flywheel?
The left side is where oil is poured into during an oil change on this one.

If this helps at all, a brand new spark plug with about an hour ride time is already super black, and I tried to start it today, and it would start up for a quick second if I sprayed starting fluid into the carb.

Any information really helps at this point. The shop says they can get it running for around $160-$200, so I'm trying any last efforts to do it myself.

Thanks again.
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stinkwheel
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Joined: 12 Jul 2004
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PostPosted: 09:22 - 29 Sep 2017    Post subject: Reply with quote

To be frank, I'd go with the $200 to get it up and running.

I'm not saying it's definately ignition timing but as I say, an electrical problem is more likely given what you've described.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Serf27
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PostPosted: 07:43 - 10 Nov 2017    Post subject: Reply with quote

A big update here!

I decided to have the shop deal with it.

I found an FCR carb for $150.

Over the course of a week or 2:

Had the shop clean it and install the carb.

They put it on, still didn't start, then said the valves needed adjustment, charged me $120 for that.

Then they said it had 40% leakage during leak down test, said it was the rings and needed a top end rebuild.

Wanted to bill me $500-$800 to do it.

I went to pick it up, dished out $430 in labor and parts and went to another shop to see what they said.

The other shop said the valves weren't adjusted properly, so they adjusted them and voila! Only $150 and only took 2 days!

Finally fires right up! I did one test run and seemed to run great.

I am very upset with the other shop, charging me $430 just for cleaning the carb and installing it, since their valve job was crap. Then trying to get me to have the top end rebuilt there.
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