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Discussion Starter · #1 ·
I’m working on this 2007 trx450er for a guy and It’s throwing me for a loop. Completely stock bike. Stock air filter, box and lid. No hour meter but he don’t ride a lot. Basically his concern was that it started loosing top end power and he always had to push start it. So I started with cleaning the carb. It really didn’t look bad. I didn’t see any jets that were plugged. But either way cleaned it and put new seals in, moose needle, needle valve, adjusted float height and moose thumb fuel screw. Put it back together and won’t start. Checked valve adjustment. Both intakes were tight. Had to drop 5 shim sizes down (.25mm) on right and just 1 shim down on left. Exhausts are good. Decompression rocker was out of spec a little tight and is now adjusted. Now it starts and runs good with choke on. Warm up and turn choke on and it dies does not want to idle. It will stay running with choke off but you can tell it seems lean. A lot of popping. Stock jets besides 148 main. So I took carb back apart looked everything over again. Blew shop air through all of carb. Put back on same thing. What’s weird is that if you put one finger over edge of air box lid hole to block it some it runs great. Telling me it is lean. Checked for air leaks around carb with carb cleaner. Nothing. Took carb back off. Put new front throttle slide and seal in. Same thing. Changed pilot jet to a 52 and main to a 150. Fuel screw 3 turns out and it runs and idles decent. Still could go up on the pilot. But my question is why is it needing to go so big on jetting to run good? Also checked compression good at 50 psi and ignition timing is good. Has anyone ever run into this before? Is it possible carb is worn out requiring richer jetting? Sorry for the long post. Im stumped….
 

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Did you do a Leak down test one it?

If you are for sure that you did set the Intake Valves at .006" and Exhaust at .011" it could have leaky intake Valves and causing it to run lean. 90% of the Time that a TRX450R/ER will only start being push started is usually due to the Intake Valves are Tight. Make sure you for sure have then set at .006 Intake and .011 Exhaust Decompressors I usually set at .006". When you Adjusted them did you adjust them on TDC with the Cam Lobes pointing to the back of the quad?
 

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Discussion Starter · #3 ·
No I haven’t done a leak down test because compression was good. But I think its a good idea. Yup intakes are .007” and .006”. Exhaust .011”. I adjusted decompressor to .021” per manual. (.010” plus right exhaust valve clearance .011”.) All while on tdc compression stroke lobes pointed backwards. It is starting right up without having to push start now. Just with choke off it is popping, sputtering and won’t idle. I will do a leak down test and see what that shows. Also wondering if I should readjust decompressor too? It does seem a little noisy at low idle. 04-05 spec is .006” plus exhaust clearance so that is still .017”. 006” like you were saying seems tight?
 

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Discussion Starter · #4 ·
Just did a leak down test. Past with flying colors. Surprisingly low at 5% leakage past the rings. Engine cold. Rechecked valve clearances. Timing. Everything is checking out.
 

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What y’all think? I I know it’s my first post but love these forums and others like it. I’m a diesel truck tech by career. And love dirt bikes quads and whatever has a engine. It’s about like being in the shop sharing brain power bouncing diagnostic ideas off each other. Nothing like it. Let’s hear your thoughts on this one.
 

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Discussion Starter · #6 ·
Went back through carb again. Triple checked it. Rechecked valves, timing. Good. Put a 125main jet and 45 pilot in in. 2 turns out on fuel screw. Runs like shit. Put stock fuel screw back in. No difference. Did a compression test and leak down test engine hot. Everything is good. I’m thinking of going back up to a 52pilot and let it roll. Does anyone see a problem with this?
 

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Went back through carb again. Triple checked it. Rechecked valves, timing. Good. Put a 125main jet and 45 pilot in in. 2 turns out on fuel screw. Runs like shit. Put stock fuel screw back in. No difference. Did a compression test and leak down test engine hot. Everything is good. I’m thinking of going back up to a 52pilot and let it roll. Does anyone see a problem with this?
Did you change the mid body gaskets? Those will cause a lean issue. I didn't see that in your list, could have missed it though to be fair.

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Discussion Starter · #8 ·
Did you change the mid body gaskets? Those will cause a lean issue. I didn't see that in your list, could have missed it though to be fair.

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Great minds think a like. I am thinking the same thing. Just got a mid body kit yesterday and gonna tear into it again. Tear it down completely and soak in some berrymans. I hope to see those gaskets tore up. Glad you are thinking same thing. What’s weird is that I sprayed the crap out of it with ether while running looking for leaks but it showed nothing. Hope it’s leaking internally maybe.
 

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If it starts a runs better with a larger Pilot then for sure go to that larger pilot because Ironically I just delt with a 06 ER at work today that had this very Similar issue... It would almost start then make a "clunk" do it till it killed the battery almost like the Spark Timing is to far advanced. I ended up playing with the Jetting and upped the pilot till it would Run right even though the AAFR was super rich like 10:1 but it did however idle good not sure why exactly, valves were good rebuilt Head), decompressor was good, carb was freshly rebuilt etc.



Yes Mid Body seal can cause a Lean problem too.

Have you checked to see if you're getting good spark?

Also is the Spark Plug black or white?

You mentioned Ether.... Hopefully you never sprayed it inside of the Carburetor? Or did not use Carb Cleaner or Brake Cleaner in the carburetor right? That can eat the Vacuum Plate Seal which can create a lean running condition it can also turn the mid Body seals into Gum and they will block up all kinds of Passages.
 

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Discussion Starter · #10 ·
If it starts a runs better with a larger Pilot then for sure go to that larger pilot because Ironically I just delt with a 06 ER at work today that had this very Similar issue... It would almost start then make a "clunk" do it till it killed the battery almost like the Spark Timing is to far advanced. I ended up playing with the Jetting and upped the pilot till it would Run right even though the AAFR was super rich like 10:1 but it did however idle good not sure why exactly, valves were good rebuilt Head), decompressor was good, carb was freshly rebuilt etc.



Yes Mid Body seal can cause a Lean problem too.

Have you checked to see if you're getting good spark?

Also is the Spark Plug black or white?

You mentioned Ether.... Hopefully you never sprayed it inside of the Carburetor? Or did not use Carb Cleaner or Brake Cleaner in the carburetor right? That can eat the Vacuum Plate Seal which can create a lean running condition it can also turn the mid Body seals into Gum and they will block up all kinds of Passages.
Interesting. This bike will start right up with choke on but with choke off it won’t idle and runs lean.

Plug is pure white.

no ether sprayed into carb. Only used it on outside of carb and boots to check for leaks.

Small amount of carb clean sprayed through out with slide and float out while cleaning.

installed new throttle slide plate and seal

finally found time to get it back apart and change mid body gaskets. I’ll let you know what I find…..
 
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