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YZF 450 tune up


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I have a '07 YFZ 450 that sat most of this is winter and got It out today. I was really surprised it started right up, after i let it run for a bit i was off. Shortly after I noticed what I would say is a sticking throttle cable. I had no time to investigate it. it would hold a higher rev and then back off when I used the clutch/brakes, but this would not always work. I was wondering if this is a common problem with the YFZ or do I sound right?

Also I had read somewhere that if your header pipe glows red that it might be a sign that your carb is not adjusted correctly to the lean side as there a tutorial some where that I could read on Carb adjustment and a Diagram of a YFZ carb?

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Dream Car Giveaway

What Bot said. Lube your cables, and check they are not getting caught up anywhere and the slack is set correctly. 450s idle high anyway, so it could be normal..hard to tell not hearing it though. Probably needs rejetted, especially if it's still stock settings.

jetting theory


Do you need a diagram for jetting? Just loosen the clamps on the boots, spin it so you can reach the 17mm cover on the bottom, remove that and you will see your main and pilot jets. Take them out and put bigger ones in (i.e. 165 main 45 pilot or whatever size works best). You should also pop the plug blocking your mixture screw and put an aftermarket one in

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I don't think that if the nut loosened up on the carb it would hold it open, it would actually make it slack and less apt to throttle response. The spring in the carb will pull the cable back when in idle.

I would definitely rejet if it is still stock (notoriously bad stock jetting), I'm about 95% sure it is running lean now. Average setting for these is usually around 165 main 45 pilot and 2.5 turns out on the fuel screw, that will get you in the ballpark.

I'd just try to google a download for the trx manual, I'm sure they are out there.

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for the trx i just like to know what im dealing with. theres no problem with it or anything. I'm an engenering student and wanted to compare the 2. The YFZ manual shows that there is 2 nuts on the throttle cable outside and inside the carb. I can pull the throttle cable ALL the way past the end of the threads and see bare cable. so the inside one has to be loose and just binding up. i would say that the throttle is held open 1/16 of the way, at random times. I'm not going to have time to open the cover and look at it till tonight. If you want to see some pictures of it, i need a lesson on how to post pics.

Edited by monsterZ914
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