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low eng pwr/new eng ticking

Old 04-26-2013, 11:07 PM
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low eng pwr/new eng ticking


My bike is running a little rich. I recently blew my frontplug. I didnít know what it was at first and took my airbox off to have mybuddy look at the carbs. It was about time to check/change plugs so I pulledthem out. Come to find out this is how they look. I never did find the top ofthe plug but I blew 100 psi of air into the chamber, then borroscoped the topend. It looked normal, (no nicks, scratches, and Xís look good). Well I put itall back together and now it doesnít sound right. Now I have a weird clickingsound with only half the power at any throttle, than I had before. It also onlytops out at 80. Anyone have any ideas?


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Old 04-27-2013, 07:05 AM
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When you say you "blew" the plug what does that mean? Does it mean it broke off? Is the contact for the electrode missing?

Have you checked the plug wire to insure you don't have the broken off part of the plug stuck in there?

Sounds like one of your cylinders is not running, can you confirm?

Last edited by RWhisen; 04-27-2013 at 07:09 AM.
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Old 04-27-2013, 07:48 AM
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We need a compression test, now. Should be 165psi each. Cam timing may have jumped a couple of teeth.
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Old 04-27-2013, 08:02 AM
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Check the timing hasn't been set 180 degrees out.
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Old 04-27-2013, 09:32 AM
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Originally Posted by Wicky View Post
Check the timing hasn't been set 180 degrees out.
I must have missed the part of his post where he said he did any work to his engine other than changing the plugs.
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Old 04-27-2013, 09:46 AM
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Originally Posted by RWhisen View Post
When you say you "blew" the plug what does that mean? Does it mean it broke off? Is the contact for the electrode missing?

Have you checked the plug wire to insure you don't have the broken off part of the plug stuck in there?

Sounds like one of your cylinders is not running, can you confirm?


The electrode was the piece that came off. If you look at the pic above, those were the 2 plugs I changed out. I know both cylinders are running because I have about half power. When I blew my plug, I had absolutely no power.

As far as a compression check I don’t have the tools to check that, but I can take it into the shop on Monday.

As for cam timing, how hard is it to remove the front head cover and check that? I removed the rear cover before when I originally had the problem but didn’t check the timing.


Really the only work I did was remove the tank, airbox, andrear head cover. I was going to have a buddy clean jets and carbs because I knewit was originally running lean but never got a chance clean to fix the carbs. ThenI decided to look at the spark plugs and realized one was pretty wet, and theother one blew the electrode off. My main concern for a while was that theelectrode was stuck on top of the piston, but I was able to verify it was not in there and that the walls weregood.

Last edited by Derek Perry; 04-27-2013 at 09:58 AM.
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Old 04-27-2013, 09:56 AM
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Originally Posted by Derek Perry View Post
The electrode was the piece that came off. If you look atthe pic above, those were the 2 plugs I changed out. I know both cylinders are running because I havesome about half power. When I blew my plug, I had absolutely no power.

As far as a compression check I donít have the tools tocheck that, but I can take it into the shop on Monday.

As for cam timing, how hard is it to remove the front headcover and check that? I removed the rear cover before when I originally had theproblem but didnít check the timing.
If you suspect a hunk of metal is bouncing around in your engine, continuing to run it isn't the best thing to do.

I have seen a piston wrist pin lock do amazing damage to the cylinder of a Yamaha YZ before. Perhaps the piece has become lodged in your valve seat and is keeping the valve from closing all the way. You can borrow a compression tester from the auto parts store.
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Old 04-27-2013, 12:41 PM
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How does this happen? I mean these iridium plugs are meant to last 100k, and I've heard of instances where people neglect them and go longer (Spark plugs? Huh? ) How many miles are on the bike? What year is it? I know the original DPR9EVX9 plugs were platinum and somewhere along the line they phased them over to the iridium ones, I'm thinking around 2001-02, so it's likely these aren't original plugs either. They were probably replaced when the aftermarket pistons went in (per your sig).

Those plugs look way older than they should, and I have a feeling I know what might be going on. Look at the crush washers on the old plugs. Notice how crushed they are compared to the new ones? That's right, they're NOT! I think the plugs may have been loose and leaking by, and by the look of the insulators I might be correct. This may have also affected your wires in a very negative way. I think there is a procedure for checking resistance of the wires but I'm at work and don't have the manual downloaded here. Looks like there's a combination of things happening here...

Now I'm starting to understand the meaning of "blew the front plug".
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Old 04-27-2013, 05:15 PM
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After some thought I think I know where the electrode might have gone. If the plug, as you say, blew out there's a good chance the compression stroke beat the crap out of the plug while it was between the head and the wire boot. That may have knocked the electrode off. Just guessing here.....
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Old 04-27-2013, 06:36 PM
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Originally Posted by Hawkrider View Post
After some thought I think I know where the electrode might have gone. If the plug, as you say, blew out there's a good chance the compression stroke beat the crap out of the plug while it was between the head and the wire boot. That may have knocked the electrode off. Just guessing here.....
Hopefully that is what happened.....

New maintenance interval...Wait till plug blows out of hole to change it.
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Old 04-29-2013, 06:24 AM
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Ah, check for PVLIR. Please use the search engine. Also, bump to the top because I'm curious as hell what happened and how this will turn out.
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Old 04-30-2013, 03:15 PM
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I was planning on doing a compression test but it is loaned out from theauto hobby shop here on base. I have to wait till I run into town to check oneout. It is a 98, and has 28k on it. The pistons were changed out around 9k. Theold plugs were iridium. The plug that blew, looks like it was only hanging onby a small amount for a while because there is residue on top of where itcracked, minus the edge where it finally broke, if that makes sense. I know itsnot PVLIR, because I originally had the problem when I put it all backtogether, I forgot put the back tube on the wrong spot, but I fixed that.


Can someone tell me how hard it is to check the timing on the front piston?

Here is the full list of mods that the owner before me did. I have had itfor almost a year and put less than 2k on it.
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Old 04-30-2013, 03:52 PM
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Download the manual in the Knowledge Base subforum. The procedure is in there for checking cam timing. That's the only timing you can check unless your crank position sensor is falling off, and then it probably wouldn't run at all.
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Old 04-30-2013, 04:01 PM
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2 Things

First it's clicking with very low power after a plug came apart. Second that part of the plug that can't be found is shaped like the curvature of valve seat and may be stuck there holding the valve open which could cause the clicking.

To test that you don't need a compressiong tester, but only a length of fuel hose. Pull the carbs and the plugs and put it in 6th gear. Turn the engine over with the back wheel and watch the intakes go closed which means all the valves are closed for the cylinder you're testing. Put the hose in the plug hole and blow breath in. If you can't blow breath past the valves and if the piston is ok then that cylinder is ok. Sometimes we have to improvise
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Old 04-30-2013, 05:36 PM
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Judging by the parts sheet, at least one of the cylinders looks to have been rebuilt.
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Old 05-01-2013, 02:55 PM
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Well everyone, looks like I found the problem. Not sure ifthis caused the spark plug to break off, or vice versa. Either way, it lookslike Iím into a lot of work and a lot of $$$$$$$$$$.


Sorry for the choppiness, I have only used the boroscopetwice.
FML.


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Old 05-01-2013, 03:13 PM
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Yep, that's the problem!

Ouch!!
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Old 05-02-2013, 01:44 AM
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While you're at it... Swap the CCT's for new ones... I think they might be going bad...

Sorry, couldn't help myself... Ouch, that smarts...
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Old 05-02-2013, 03:39 AM
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Ouch! A colonoscopy without sedation would be less painful!
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