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terryg

05 WR450 detonation - need help

15 posts in this topic

I'm trying to find the source of the ping/detonation I have with my 05 WR450. It knocks and pings quite loudly- just as the throttle is opened when the bike is hot and engine is under moderate load at low rpm. Just pulling out of the pits as the clutch is released will produce the rattle sounding pinging sometimes. Current settings:

MJ = 168, up from 165 stock

PJ = 48, up from 45 stock

Needle = stock non-adj 05 needle

Zip Ty fuel screw - various settings with no real difference

AIS removed with TT kit

Snorkel removed

Throttle stop removed - actually YZ stop installed

Grey Wire cut

1000 - 1,500 feet elevation

The bike also exhibits the often mentioned snatchiness on the highway at 50mph with little difference when disconnecting the TPS.

I tried the JD jet kit needle as appropriate for altitude and temperature and it did not seem to have any improvement and may have been worse with the pinging extended some into the midrange - which does seem a bit flat as well.

Thanks for the help. One thing I may do is get some race gas and see if it goes away so I can isolate the problem as detonation and not chain slap.

thanks much, Terry

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You didn't mention what you were running for gas but you should try another brand of 93 octane. Not all gas is the same even if it has the same octane rating and it's possible you got some that was contaminated.

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I think its gas and timing that cause preignition. Like moto5 said, I would drain the gas tank and fill it with some new 93 octane. If that dont work I would put a timing light on her.

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Thinking more about my detonation question. Do you guys think that doing something with the accelerator pump to get a bigger squirt right as I open the throttle would help? It seems like it is just momentarily too lean right as I get back on the gas.

tks again, Terry

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Have you adjusted the 'slop' from the Accelerator Pump (AP) linkage.

Also, if you slide the carb from the engine boot and stroke the throttle, do you get a AP squirt?

If your getting detonation just pulling away from a stop check the AP circuit. I never heard of a diapharam failing but I guess it could. The AP should provide the fuel to richen the intake charge in the situation your describing.

Different fuel is a good idea too.

Read this - http://www.thumperfaq.com/ap_mods.htm

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Mine has the same things as your's done to it and it did it till I bought gas at a different place. It still makes a little noise. I'm going to start mixing 93 with 112 and see what happens.

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After riding about 50 miles last summer I dropped down into a small mountain town, gassed up (with premium) and had the same symptoms as you as well as the motor was running very hot. It went away with some good known premium gas so I thought maybe the premium fuel was actually just regular grade or some old bad gas. Lots of carbon build up can cause detonation also.

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I would look for an intake leak. AIS removed? if so, then are all the plugs on? Intake boot loose?

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Just another thought...when I buy gas, before I start pumping into my bike, or gas can, I run a couple of gallons into my truck. That empties out the low octane gas left in the pump and hose from the last customer, and assures that I get all premium (93 octane) in the gas I'm putting in my bike. My '05 detonated a little on 91 octane, but does OK on 93...if I follow the above procedure. If you fill your bike directly from the pump without doing this, you could be getting 1/3 - 1/2 gallon of someone else's 87 mixed in with your two gallons of 93!

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I would look for an intake leak. AIS removed? if so, then are all the plugs on? Intake boot loose?

That's the other thing I was thinking, if you have lean condition from a slight leak that would surely cause detonation. Also if you are running on the hot side that would cause it. I would bet it is the gas though.

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That's the other thing I was thinking, if you have lean condition from a slight leak that would surely cause detonation. Also if you are running on the hot side that would cause it. I would bet it is the gas though.

I was wondering if you could explain why a lean condition would cause pre-ignition(detonation).?

I can see heat causing carbon deposits to glow red, causing pre-ignition. And a lean bike will run hot, but a lean bike usually wont leave carbon deposits either.

fuel/air mixture wont cause pre-ignition(detonation).

Its caused either by the spark plug firing to early(ignition timing) or your fuel being unstable. Fuel will become unstable and and volatile at super high compression, an actually ignite on its own. Thats what the high octane fuel is for, to stabilize the fuel for the high compression.

In the event that there is carbon deposits causing the fuel to ignite pre maturely, its probably time for a tear down :thumbsup:

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Thanks much for the ideas. Will try some better gas first and then check the AP stuff. This is a new 05 450 that has pinged from new. Still only have about 325 miles on it so it should not be too carboned up yet and it has pinged from the start.

terry

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Terry, I suspect your getting chain slap. With the compression ratios these have (yours is like 12.3:1) they do rattle at lower speeds, mainy from the gearbox and chain area from rotating slow through the compression stokes. This tends to make it all "chug" and rattle. This isnt noticed if the compression is greatly reduced (and thats not an option as it robs power) or if the engine sppeds are increased. This will allow it to go through the compression stroke without feeling the power pulse as bad. I have an 04, compression ratio is 12.5:1, run 92 pump gas, zero ping, rattle etc. But at lower speeds, I do get the chain slap.

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I was wondering if you could explain why a lean condition would cause pre-ignition(detonation).?

I can see heat causing carbon deposits to glow red, causing pre-ignition. And a lean bike will run hot, but a lean bike usually wont leave carbon deposits either.

Lean, does in fact, create extra heat. A rich engine will actually cool things down.

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I was wondering if you could explain why a lean condition would cause pre-ignition(detonation).?QUOTE]

For one thing oxygen is much more explosive than gas, combine that with the additional heat and you get detonation. Left unattended it will burn a hole in your piston. It doesn't have to be from a leak either. I've seen people swap jets leaning too far and things get hot. Most bikes are lean from the factory to get better emissions numbers.

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