[SickNasty]

Hi guys my name is Tyler and this is my first post. I just bought a 99 400ex and it was pretty much stock besides a slip-on and intake. Besides being hard to start it ran fine before I pulled it apart.

Anyway, me and a buddy (TorqueDaddy) rebuilt both our top ends with a 86mm 11:1 piston and a stage 2 hot cam. Put everything back together, and it fired right up....just lacks power throughout the whole throttle. We assumed it needed jetting so messed with that quite a bit and got rid of the slight bog it had. Now it seems to start and run fine...just has about half the power of my buddys 400ex.

While it might need further tuning with the carb/jets...it just doesn't seem like thats the issue. There is no bog anymore...just doesn't pull! Could it be clutch? valves? What do you guys think?

Thanks in advance!

 

[SickNasty]

Never smoked, and have had multiple plugs in. I will check compression again but it was good after it was put together. Thanks for the reply. Anyone else have any ideas?

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[SickNasty]

Both of us have a stock intake with K&N filters. I used honda GN4 oil but who knows what previous owner was using.

 

[SickNasty]

I think the timing looks good...is this how it should look?

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[SickNasty]

Oem carb with keihin jets, 42 pilot and 175 main. Hasn't had any backfire or smoke just bogged/cut out until we changed the jets. I have been through the whole carb and cleaned it twice.

It could still be a jetting issue but we have gone up and down in jets and swapped carbs and it still has a seemingly unrelated lack of power...

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[SickNasty]

Found this on another thread..... something to check. Also was the tensioner engaged when you took the pics?

"look right behind the cam lobe nearest to the sprocket. If there is a small 4mm hole with nothing in it, that's your problem. There must be a pin and spring in it to hold the anti reverse device on the camshaft. If the pin is not there, the device is turning with the cam and your right hand exhaust valve only closes every second turn."

Tensioner was engaged, and there is a small hole in the head casting near the last lobe. Isn't that for the decompression pin/spring for easier starting? Thanks for all the replies

 

[SickNasty]

I just looked at your photos of the timing marks on the sprocket and the flywheel and found your problem.

The camshaft is installed using the wrong mark on the flywheel... you are using the two maximum spark advance marks on the flywheel, when you should be using the Top-Dead-Center (TDC) mark.

There should be a single timing mark on the flywheel labeled "T".
Line up that "T" mark with the mark on the side cover (thru the window where you removed the plug), then install the cam sprocket on the cam so that the sprocket mark is even with the top of the head and snug up the sprocket bolts. Make sure that both cam lobes are facing DOWN when you do this.

Then go back and recheck all of your timing marks for proper alignment (they should match closely). Once you are sure you got it right, tighten up the sprocket bolts, install the chain tensioner and the rocker cover (a thin coating of hondabond or yamabond 4 on the alcohol wiped surfaces) and break it in easy for a bit...

That's the only "T" that I could find. I've checked a few times. There is some dashes then an F and then the T with the line above it. It's in one of the pics that I posted

 

[SickNasty]

Hard to tell in the pic but are the lobes totally facing down? They look spun a little to the left.

Yes they are slightly turned. I thought it seemed weird too...but the sprocket is lined up with the head and it doesn't seem like it could be put on the cam shaft any other way

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[SickNasty]

Literally just checked this after putting my head cover back on...?
So how would I set the cam then? How should it look? Can the sprocket go on the cam wrong? I'm at TDC, and the marks on the sprocket were there, I cant see how it could go any other way

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[SickNasty]

Here is a better picture with lobes down, and all 3 marks on the sprocket showing

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[SickNasty]

@Carolynskiii
Me and TorqueDaddy compared our hot cams and they are the same, we are going to adjust valves and then pull clutch cover off and look at that.

Thanks for all the replies guys...will keep you posted

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[SickNasty]

Me and @TorqueDaddy just put everything together after adjusting valves and putting the new clutch in and she rippppps!!! When we checked the valves the intake was way tighter than it should have been so we are pretty sure that was the problem.

 

[SickNasty]

Not sure what it was just glad to have it running good! The valves were definitely tight but the clutch plates also seemed worn.

Thanks again for everybody's help.

 

[SickNasty]

They were tight...I couldn't move them up and down at all from TDC. It also started and idled great before I took anything apart. Wish I wouldn't have done them both at once so we would know for sure... The only reason I didn't adjust them was because for whatever reason, my flywheel would spin past TDC on the compression stroke every time. After putting it together this time it lined up fine!

 

[SickNasty]

Thanks @retro and @SlammedRanger.

I'll be sure to check valves again soon and play with the jetting to make sure its tuned right.

 

[SickNasty]

Hi guys, I have good news and bad news.

Bad news is 10 minutes into my 1st ride after "fixing" my problem...the quad went back to exactly the way it was...total lack of power.

Good news is we may actually find out what the problem was now!

When it finally ended up working (for 10 minutes), we put new clutch discs/springs in, adjusted the valves, and I RE-cleaned the carb. I have already re-checked the valves and they are adjusted correct.
Any new ideas? I plan on pulling the valve cover off and inspecting the valves. What should i look for? could a bent or stuck valve be the cause? How can I check them to make sure they all function right?

 

[SickNasty]

Ok I'm still confused because this definitely wasn't the problem before but I took the carb off and heard some rattling and when I took it apart the slide was stuck and the 2 tiny screws that hold the needle down came out...

Put it back together and it's is running great again. I think it is lean so I am putting a bigger main in.

It must have been the valves and when I took it for my 1st ride the slide got stuck? Couldn't have been the slide the whole time...

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