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Crf 450 Hard start after rebuild

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I have a crf 450 2004,

( I'm no mechanic so please bare with me ).

A couple of weeks ago decided to mess around with the carb as it would die after 20-30 seconds when idling. I pulled the needle out at the top of the carb and the pilot jet out of the bottom in the bowl. Cleaned them, put them back in and it wouldn't start at all just backfiring all the time. So I took it to a shop and I was told it needed a rebuild (pistons and conrod, along with gaskets).

After the rebuild the mechanic at the shop kicked it over but told me I needed to have the choke out, half throttle and use hot start, for the life of me I can't get it going at all, just more backfiring.

Does this sound normal? When cold it used to start good with the cold start technique but now nothing.

Any help would be appreciated.

Thanks

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Mine starts cold first kick with choke on No fiddling with throttle or hot start at all,

If it hasn't run since you paid to get it rebuilt I would take it back since it sounds like he fixed something that wasn't the problem

First thing that comes to mind is timing or valves not set right or decompression not set right or something is plugged in the carb or not set right.

Do you have a service manual?

Edited by darren013

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You messed up something in the carb, if it ran fine before you cleaned the jets then it was fine, I'm not totally sure that rebuild was necessary, id check your float height & needle position

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I have a crf 450 2004,

( I'm no mechanic so please bare with me ).

A couple of weeks ago decided to mess around with the carb as it would die after 20-30 seconds when idling. I pulled the needle out at the top of the carb and the pilot jet out of the bottom in the bowl. Cleaned them, put them back in and it wouldn't start at all just backfiring all the time. So I took it to a shop and I was told it needed a rebuild (pistons and conrod, along with gaskets).

After the rebuild the mechanic at the shop kicked it over but told me I needed to have the choke out, half throttle and use hot start, for the life of me I can't get it going at all, just more backfiring.

Does this sound normal? When cold it used to start good with the cold start technique but now nothing.

Any help would be appreciated.

Thanks

Dude.... He told you wha?! Hotstart? throttle half way? From the sounds of things you met somebody that absolutely scammed you for your money and had ABSOLUTELY no clue wtf he was talking about. I'd honest be surprised if he did anything internally to your motor as it sounds he has no clue how your machine even works. To start with The hot start lets air in the carb... It's for when the motor is HOT. If you are trying to run it with this open the it would explain the backfiring. all the air from that would lean out your air/fuel mixture causing it to backfire/pop and run like shii. Make sure your hot start lever is completely closed. Hopefully you put the needle back to how it originally was. The PILOT jet you cleaned? Did you blow compressed air through it? Could you hold it up to the light and see through it at all? It's a small small hole and usually it's about impossible to clean because the hole is so small and anything can get stuck in it. If you can't see through it at all it's well worth the five bucks to just replace it. I personally prefer JDjetkits and/or the rebuild kit is 17 bucks on eBay which comes with the factory jets. Next your air fuel screw. Screw this completely in then turn out 1 and 3/4 complete rotations.... Make sure your rubber boots that connect carb to motor are tight. Make sure gas is good, 93 octane of course. Choke out and yeah if you can't get that baby to fire after checking all that I might want to get ANOTHER mechanic to take a look at what your dude did with the motor. Hope you get somethin from this.

Sounds like a nightmare bro, Goodluck!

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Thanks for the reply's.

The mechanic did start it at the shop, and showed me the technique he used to start it, but once I got it home I could not get the dam thing going. I tried every way I could think but no joy.

It was never like this before the rebuild and after spending a lot of cash on it, I thought it would start up fine.

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Thanks for the reply's.

The mechanic did start it at the shop, and showed me the technique he used to start it, but once I got it home I could not get the dam thing going. I tried every way I could think but no joy.

It was never like this before the rebuild and after spending a lot of cash on it, I thought it would start up fine.

I'd think that if it was running then the motor is sound. The technique to starting it is fishy tho. I recommend the JDjetKit. Their kind of pricy but the tech support is incomparable. Order the kit and email them tell them exactly what you have and they will tell you exactly how to build your carb for what you have and where you are. Bottom line is the only thing you should have to do is pull your choke out and kick... The only other thing it very possible could be is your idle screw, if its set low that would explain the throttle half way part. This is the almost dime size piece on the left side of your carb that has a line down the middle perfect for a large size flat head. Turn that clock wise to turn your idle up, play with it some but count how much rotation your adding incase this does not work so you know how much to reverse it incase this dosnt work.

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When i took it to the shop in the first place, I told them that I had fiddled around with the carb and that it wouldn't start just backfire. So they reset the carb as it should but they could only get the bike to start by bump starting it, and when it did start it sounded rough.

They said there was play in the con rod when inspected and needed replacing along with the piston and rings. I'm happy the work has been done as I don't know when the bike had its last rebuild, but unhappy that it doesn't start as it should, and that being the reason it went to the shop in the first place.ImageUploadedByThumper Talk1378627043.155404.jpg

ImageUploadedByThumper Talk1378626964.831876.jpg

ImageUploadedByThumper Talk1378627016.697932.jpg

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When i took it to the shop in the first place, I told them that I had fiddled around with the carb and that it wouldn't start just backfire. So they reset the carb as it should but they could only get the bike to start by bump starting it, and when it did start it sounded rough.

They said there was play in the con rod when inspected and needed replacing along with the piston and rings. I'm happy the work has been done as I don't know when the bike had its last rebuild, but unhappy that it doesn't start as it should, and that being the reason it went to the shop in the first place. ImageUploadedByThumper Talk1378627043.155404.jpg

Well.. That shouldn't give you a hard time getting it right after all that work.. Sounding rough could be a lot of things but backfiring in most cases means either it's running lean, which the pilot screws on these things clog all the time and that provides about 1/3 of your fuel and will cause that with a quickness. Once again that's a five dollar part and a five minute job or the less likely cause is a exhaust leak. Either way if they cannot start the bike without holding the throttle. doing no more then pulling the choke and kicking, then something's up. They were quick to get you to pay big bucks for a piston and such, somethin minor like getting the carb right shouldn't be a issue at all. I'd carry it back up there and not pay a penny more. Shouldn't be a problem at all.. Unless they were just trying to scam you the entire time.

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By the way. If you could still kick your bike over and if the exhaust wasn't kicking out black smoke then that was the least of your troubles. Yeah it might could of used one but that still has nothing to do with your original problem of it backfiring. And for them to tell you that they would of had to remove the whole top half of your motor.which before that they should of resolved this carb issue. Sounds to me like you Hooked up with some shady mechanics. Anyways Goodluck!

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And if you have to bump start it to get it to run then nine times out of ten its you need to get your valves shimmed.

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I'll have a go at starting it later but if its still not firing up then ill be ringing the shop Monday morning. I don't want to touch anything myself until I've spoke to the mechanic first.

Thanks for the reply's

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Worth a try - throw a fresh plug in it (extra oil at rebuild on piston=fowled plug).

Check the resistance on the plug coil.

We just went through almost the same saga, shimmed valves, ran compression, went through carb 3 times on our 150R, wound up being the coil.

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To be honest I'm hoping the shop will sort it out after I've spent a lot if cash on the rebuild, and it is exactly the same before it went in.

I've tried it today but still nothing but backfiring?

After the work, it thought it would kick over as normal?

Thanks for the feedback.

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I have a question.

After the rebuild my bike has had, should I have good compression?

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I have a question.

After the rebuild my bike has had, should I have good compression?

Yeah dude you had a new piston kit installed so that's new rings on your piston. Compression should be 60-80 pounds.

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Yes it should be as it came new from the factory!!

Aslong as the valves are sealing up and timing is correctly set.

I wouldn't mess with it, take it back and get the shop to fix it even if its a problem that has nothing to do with what they did let them find & fix it

Maybe suggest they start by a complete rebuild of the carb and go from there what goods a freshly built bike if you can't start it

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Thanks for the quick reply.

I don't have the tools or know how to test it to get the measured pounds, but should the kick start be harder to push down?

As you can tell I'm not much of a mechanic, just trying to learn about these bikes.

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I've taken it back today and the mechanic tried to start it and couldn't get it going, only backfiring. So they are having a look at. I don't think there's much difference if any in compression before it went in?

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The compression might have be ok before you took it in but if the bearings were out of spec and piston had signs of wear you did the right thing to have it freshened up before something let go.

I'm sure they'll have it running great in no time

Next time you have a motor rebuilt ask for the old parts back in the new part boxes then there's no doubt what they did or didn't replace,

I had a new top end installed in my 450 and I got it back and it was a beast to kick over, upon further investigation the valve timing was off

I fixed it myself and won't have anything else done at that dealership!!

I only sent it on because I was so busy with work and wanted to ride the next weekend

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