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07 won't start after shimming valves

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So I've lived up to my username and botched what I thought should be an easy job. I'm really hoping somebody can help me out cause I've hit a brick wall.:banana:

Last fall I drained the tank and carb for storage and parked the bike. I decided over the winter to check the valves since I know the previous owner never did. Three of them were just slightly out of spec so I got myself a shim kit to do it myself.

Generally I'm not a complete dumbass but I really screwed the pooch on this one. Basically while doing the formula I forgot one number was a negative and re-entered it into the equation as a positive, giving me the wrong new shim size. I realized this once I put it back together and the clearances were way off. Time to take the cam assembly out and try again...

At this point I was flustered so what did I do? After removing the bolts from the cam chain sprocket I manually turned the engine over one more time, without pulling the sprocket off of the cam :lol:. Turns out I over rotated and snapped the tab off the decompression shaft that moves the plunger (yes I found the broken piece on the floor).

$115 and a new decompression shaft later I'm ready to put it back together again. This time I did the math right and put the new shims in, clearances checked out good so I thought I was in business. I put fresh gas in it and kicked and kicked and kicked, no dice. Also, when I reach TDC it gets so hard to kick I can stand on the kickstarter and it won't move right away (200 lbs.). I never had trouble kicking it over before but now it's to the point I don't have enough strength to move this thing once it hits TDC :banana:

Oh yeah, it didn't start being a real pain to kick until after I replaced the plug. I went by the service manual even though I thought it sounded outrageous (16 ft. lbs.) but I figured Honda would know what they're talking about so I went for it. It's tougher to kick now, but it still wouldn't fire before I did this.

I checked the plug, I have a spark.

I cleaned all the jets, fuel is being delivered.

Timing is on, all cam/sprocket marks are aligned perfectly.

I can't even get a sputter like it wants to kick over.

Anybody out there in TT land have any ideas? Thanks to anyone who took the time to read my short story. Anyone who has any ideas to help me get this thing up and running would be appreciated more than you can know.

I really miss my 2 stroke right now...

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Well assuming that the cam timing is indeed correct I would say that the shft to the decomp pin is not installed correctly.take the valve cover off and see if you can see the decomp pin protruding from the cam,and if it is see if working the lever on the cam sprocket retracts it.

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Thanks for the suggestions. I'm sure the cam timing is correct because the chain never once came off the sprocket, each time I immediately zip tied it up to the frame. I also tried the decompression weight (I think that's what it's called, the piece you mentioned) motion and it moves smoothly. Not at every position throughout the stroke though, I only tested the movement at TDC.

I even pulled the camshaft assembly off and tried to install the decompression shaft backwards to see if I could have screwed up that way, nothing would line up when I tried doing it opposite of how I have it now.

I swear I've gone through the service manual 50 times and every picture and description matches what I see on my bike. That's why I'm so puzzled.

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Youve missed the decompressor lash somehow. If youve got too much decompressor lash, it wont let enough out of the cylinder and you end up with your situation. And never assume the timing is correct. Just because the chain didnt come off the top sprocket, that doesnt mean it didnt come off the bottom one, even though thats pretty tough to do.

Start at the front of the horse. Check everything as if someone just brought it to you because they didnt know what was wrong. Ive had to do this a couple times and everytime I found a mistake that I assumed was correct.

Start at checking the valve lash per the book, as if you just took the valve cover off. Take a breather first though. When you get a bent out of shape, your brain turns off and you miss stupid shit...

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Thanks Shawn. Could you possibly elaborate on the decompressor lash? I've seen mention of this elsewhere but can't for the life of me find a reference in the manual to see what the clearance should be.

I'll check the timing once again to make sure, but I'll definitely be taking a break to watch the SX race tonight. Just like you said, I need to stay out of the garage to clear my head and rethink everything.

Edited by ithinkibrokeit

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I agree with shawn, youre decompressor gap is set too big and not decompressing the motor enough, or at all. very common problem it seems.

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I had a KX250F an 07' and redid the valves, and figured out that I had a bad stator. Ordered one from electrosport.com and voila, it started right up.

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Well just today i dealt with the same thing. Just got done putting a brand new head (brand new) on my 04 crf450, along with a athena 490 kit. When i got it all together, i couldnt hardly kick it over. Sure enough the decompressor clearance, lash or gap was about double the .014 that the service manual calls for. Adjusted it and voila it kicked over easier, but due to 490 kit, harder than normal. Now the problem i thought and told was the head being bad, turns out to be something else. My bike is popping really bad out the exhaust. And when it shuts off it sounds like one last explosion of unburnt fuel. It just pops and snaps when it runs and is harder than hell to get started. It was doing all this before i did all this 1500 dollars worth of work, and now its still doing it. I double checked the valve clearence and checked my head pipe for cracks and see nothing that would cause this. does anyone have any advice?????

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Well just today i dealt with the same thing. Just got done putting a brand new head (brand new) on my 04 crf450, along with a athena 490 kit. When i got it all together, i couldnt hardly kick it over. Sure enough the decompressor clearance, lash or gap was about double the .014 that the service manual calls for. Adjusted it and voila it kicked over easier, but due to 490 kit, harder than normal. Now the problem i thought and told was the head being bad, turns out to be something else. My bike is popping really bad out the exhaust. And when it shuts off it sounds like one last explosion of unburnt fuel. It just pops and snaps when it runs and is harder than hell to get started. It was doing all this before i did all this 1500 dollars worth of work, and now its still doing it. I double checked the valve clearence and checked my head pipe for cracks and see nothing that would cause this. does anyone have any advice?????

id bet its your jetting but thats all I can tell you, im not sure if its too lean or too rich. id guess too rich but im no jetting expert. im sure someone will tell you exactly whats wrong.

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check timing again sounds like you are 1 tooth advanced 07 switched to centrifugal release timing always seems to move a tooth or 2 no matter how you secure it.GOOD LUCK.

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Its sounds like your timing is off(for hondaor77)

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Might be off base here, but in 2007, Honda did away with the adjustable decomp and went with the non adjustable centrifugal decomp. I did the exact same thing with my bike including snapping the pin off. I would bet that your problem lies with either your installation of the decomp shaft or the return spring on the decomp weight on the sprocket is either broken or popped off.

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mine is actually an 04. I have so much money into this thing i cant ever sell it, so i keep just repairing and replacing parts. All the stuff i would need to do to a new bike (rekluse, stabilizer, subtanks and so on would all have to be purchased again). My timing is spot on. The jetting could be the issue but it wont even hardly start. Which jet does the carb use to start the bike? When i tore it apart, the guy who had always adjusted the valves for me said that the last time he adjusted them was the last time he would be able to and then i would need a new head. So i assumed that the exhaust valves had tightened up and werent closing fully. But complete new head from big bore thumpers and still have the same issue. Went back to stock jetting and still wont run without popping.

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mine is actually an 04. I have so much money into this thing i cant ever sell it, so i keep just repairing and replacing parts. All the stuff i would need to do to a new bike (rekluse, stabilizer, subtanks and so on would all have to be purchased again). My timing is spot on. The jetting could be the issue but it wont even hardly start. Which jet does the carb use to start the bike? When i tore it apart, the guy who had always adjusted the valves for me said that the last time he adjusted them was the last time he would be able to and then i would need a new head. So i assumed that the exhaust valves had tightened up and werent closing fully. But complete new head from big bore thumpers and still have the same issue. Went back to stock jetting and still wont run without popping.

what is your decompression arm clearance?

im in the same boat as you, too much money into the bike to sell. I have over 20K into it :banana:

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She Fired!! :banana:

Thank you all so much for reminding me to not overlook the simple things. I guess it's true what they say about assumption being the mother of all f*** ups.

It was the timing. Somehow it must have come off the bottom sprocket the last time I pulled the cam sprocket off cause I know the first couple times I checked and it was dead on (I pulled everything off WAY too many times for this project). Ah well, once I got it corrected this time it fired up second kick.

:lol:

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mine is actually an 04. I have so much money into this thing i cant ever sell it, so i keep just repairing and replacing parts. All the stuff i would need to do to a new bike (rekluse, stabilizer, subtanks and so on would all have to be purchased again). My timing is spot on. The jetting could be the issue but it wont even hardly start. Which jet does the carb use to start the bike? When i tore it apart, the guy who had always adjusted the valves for me said that the last time he adjusted them was the last time he would be able to and then i would need a new head. So i assumed that the exhaust valves had tightened up and werent closing fully. But complete new head from big bore thumpers and still have the same issue. Went back to stock jetting and still wont run without popping.

Did you spin a cam? It really sounds like a timing issue, esp. if its hard to start and popping when you give it gas and such. Sorry if im stuck on that lol

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mine is actually an 04. I have so much money into this thing i cant ever sell it, so i keep just repairing and replacing parts. All the stuff i would need to do to a new bike (rekluse, stabilizer, subtanks and so on would all have to be purchased again). My timing is spot on. The jetting could be the issue but it wont even hardly start. Which jet does the carb use to start the bike? When i tore it apart, the guy who had always adjusted the valves for me said that the last time he adjusted them was the last time he would be able to and then i would need a new head. So i assumed that the exhaust valves had tightened up and werent closing fully. But complete new head from big bore thumpers and still have the same issue. Went back to stock jetting and still wont run without popping.

If you had the slide out of the carb for any reason, Id bet you got the vacuum release plate back in up side down.

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Yeah im probably twenty k into mine or more if you include buying it. My decompresser clearence is exacly .014 like the manual says. my cam sproket is right on the mark, and the inspection hole marks are lined up just like the manual. It starts and runs but its a bear to get it there. It has good throttle response and all, just backfires and pops. When i rode it before all the rebuild, it would stop popping after a little bit of throttle in second gear. Then as soon as you let off the throttle it would pop and snap on deceleration. Havnt rode it since the rebuild but it sounds the same at startup. GSCX what did you mean by spin a cam? It has a brand new stage 3 cam in it and didnt before.

My 2-stroke offroad monster is getting alot of action right now, but i miss the torque of the 4-stroke. I built this cr285 to match my 450 With the rekluse and stabilzer and all that crap so that i could go to a race and have a backup. I have like ten grand into this cr and im beginning to like the ease of maintenence, but that damn thing is giving me fritts as well. I have been told the airstriker carb will fix it and its on its way so we will see. just alot of tweaking and tuning and not alot of riding lately. GRRR

Edited by hondaor77

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Well if it didnt stop backfiring after you put the cam in it thats not your problem, but sometimes they will spin on the bearing and it will make the timing go off. And i know it sounds stupid but did you make sure your pilot circuit is clean? I mean like really clean. If it stops doing it when you give it gas it makes it sound like your pilot

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If you had the slide out of the carb for any reason, Id bet you got the vacuum release plate back in up side down.

Definitely check this.

On those FCR flatslide carbs, I have put the vacuum plate in upside down more times than I can count. The bike will be difficult to start, but it WILL still run, and it will run exactly like you describe.

I know this from experience!

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