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Bike really hard to start !

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My bike is really hard to start,

I checked the valves and they are perfect still, The engine was re-built about 30-40 hours ago and was maintained good and all seems fine...

So it must be a problem with the carb i assume ?

The only change i made was putting a 45 pilot jet in (Was 42), But i only changed that out because it was hard to start so i don't think there is a problem there.

I also took the spark plug out when checking valves and looks very old so could a new spark plug solve my problem ? A weak spark maybe ?

Thanks

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It's doubtful that it's the plug. If it's an iridium plug, they last forever. What year is the bike?

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It's doubtful that it's the plug. If it's an iridium plug, they last forever. What year is the bike?

The bike is a 2008, Do they come stock with iridium plugs ?

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The bike is a 2008, Do they come stock with iridium plugs ?

Yes. Iridium plugs are exceptionally good. Cars with iridium plugs do not require replacement for 100,000 miles. I'd love to see one of these bikes with 100k on them. I've never had a bike with problems that had a plug related issue. I know there's exceptions to the rule, but personally I've never seen it. I'd bet a stator before a bad plug on a no start or intermittant spark issue.

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So what could be the problem then ? Is there a good chance this is carb related ?

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This is the tough part of trying to troubleshoot something like this and not having the bike in front of me. Yes, it could very well be the carb. I would check it first, but it could be a stator, pickup, CDI controller and so on. I'm sorry that I can't tell you exactly what the problem is. If you want to bring it by my house in the US, I can tell you exactly what's wrong with it! LOL! The issue you're having is not cut and dry like a no start with a set of bad intake valves.

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Oh something i remember was that when i finally do get the bike started the idle is rough (Varying in RPM) for about a minute....

That might just be because it is cold but could that be a sign of where the problem is ?

Also to clean the carb. Where do i spray the carb cleaner ? What do i avoid spraying ?

Thanks

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The RPM's going up and down relates to a dirty carb. You really need to remove the carb to do the job right. Carb cleaner will help and you will need compressed air also. The most critical part you cannot spray with the carb cleaner is the throttle slide. You must pull the slide out and when you dothe job. Make sure you pay close attention to the plate that sits on the slide. It's critical to make sure that it goes back together in the same direction it came apart. There's a very delicate seal that seals the plate to the slide. If it's damaged in any way, replace the seal. You can't get just the seal from Honda, but Yamaha sells them separately. The smartest thing to do is replace the pilot, main and leak jets with new. The leak jet needs to be changed out to a 45, there's probably a 70 in it (unless you have an adjustable leak jet already in it). You should have a 42 pilot and a 172 main. Let me know the altitude so I can confirm that's correct. If you don't have an adjustable air/fuel mixture screw, it would be a great time to put one in.

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Has it always been difficult to start? Check your starting procedure also. Makes a big difference. A lot of people say not to touch the throttle when you start a cold engine. If you twist the throttle a couple of times before you kick it over it helps to prime the engine with gas. The colder the weather gets the more twists it takes(up to 5 or 6). Just dont twist it while your kicking. Plus Charlies jetting recommendation.

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Any chance you are running an aftermarket fuel screw? I found the end of my MSR fuel screw's anodizing had partly flaked off and collected some debris - blocking the fuel screw delivery port. I cleaned up the tip of the fuel screw with 800 grit sand paper and it started as it should.

Two other things to check:

I have also lost the tiny O-ring that sits on top of the tiny washer on top of the fuel screw spring and instead of pulling fuel in through the fuel screw circuit - the carb just pulls in air, making it almost impossible to start or get a steady idle.

Since you swapped out the 42 for a 45, I suspect a plugged pilot was not the problem, but the 45 may be too rich and getting a decent idle will be a challenge because you may have to run your fuel screw in all the way to get the right low speed fuel flow.

And the last thing I did was modify my '09's decompression lever as per Ron Hamp's directions. You basically grind off a part of the decompressor lobe to let the valves close earlier during starting to build compression quicker. Made a huge difference in ease of starting...

Here is a link to the thread:

http://www.thumpertalk.com/forum/showthread.php?t=656459

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The smartest thing to do is replace the pilot, main and leak jets with new. The leak jet needs to be changed out to a 45, there's probably a 70 in it (unless you have an adjustable leak jet already in it). You should have a 42 pilot and a 172 main. Let me know the altitude so I can confirm that's correct. If you don't have an adjustable air/fuel mixture screw, it would be a great time to put one in.

I'm at 0-600 feet and temps around 46F - 55F

Jetting now,

Pilot - 45

main - 178

leak - 70

Thanks for all your help, I really appreciate it

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Go with the setup I reccommended. Worse case, you can always change the pilot, but everything else will be fine. Also, the needle should be in the 3rd or 4th position. Count down from the top 4 slots and try it there. If it seems a bit rich in the middle, move it up 1. That should do it. The bike is going to be more responsive all the way around. It's going to feel totally different in a good way!

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Go with the setup I reccommended. Worse case, you can always change the pilot, but everything else will be fine. Also, the needle should be in the 3rd or 4th position. Count down from the top 4 slots and try it there. If it seems a bit rich in the middle, move it up 1. That should do it. The bike is going to be more responsive all the way around. It's going to feel totally different in a good way!

I found the problem,

The main jet has cracked and was barely attached (I guess i must have tightened the jet too tight)

It gave me a chance to clean the carb out though, I will try the jetting you recommend...

Thanks for all the help

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