Yfz 450 Help.

[joshuafrazier]

Yesterday I traded my Blaster For A YFZ. When we got the yfz home it would start but not stay on. The last time it started, i rode it 50 feet and it started leaking engine coolant. The hose has a fried o-ring. Once i get that fixed, im going to replace the hoses, drain oil-gas-coolant then add new. Change spark plug, and either clean the air filter or replace it. Does anyone know if the pro-filter k&N can be cleaned? Then im going to clean the carb and rejet because i think its wrong. Does anyone know how to fix the hard starting, or were to start?

The bike has a new chain in the engine, rechambered head with gaskets, white bros carbon slip on(POS), pro filter with K&N and airbox lid removed. Can someone help me with all these problems? Thanks.

 

[BugsBunny]

I would not rejet the motor till you can run it & do a plug check - best to get it runing properly first, that would be my priority

 

[joshuafrazier]

the carb needs to be cleaned because its been sitting, and it backfires so the jets are wrong, correct?

 

[Blaner]

ah gracious, these things can be tricky! they make use of an accelerator pump which squirts more fuel when you punch the throttle or increase rapidly. this system is timed. if the timing of the fuel squirt is wrong, the bike will bog as it suddenly gets an injection of fuel at the wrong time. there is a method of sticking a 4mm object, a screwdirver with the right diameter works well, under the slide and then adjusting the cable onto of the carb untill the slide sits 4mm off the bottom. i cant quite remember the whole procedure and if its 4 or 3mm but its very NB to get this right or else your jetting will NEVER be right!

find yourself a manual and maybe someone else can chime in with the full story

 

[joshuafrazier]

it needs alot of little things as well. I could very well end up spending more money in aftermarket parts than i did paying for the bike.

 

[Blaner]

it needs alot of little things as well. I could very well end up spending more money in aftermarket parts than i did paying for the bike.

thats often the case when you get a new bike. seems so many people dont bother to take care of their machines and then sell them to guys like us who actually mind if the thing doesnt run!

 

[Kgibson]

yfz or yz....u said it had a rechambered head which is a 2 stroke thing. If its a 4 stroke it sounds like the valves need shimmed. Tight intakes cause hard starting and tight exhaust can causea backfire/or ur lean/or what blaner said ...lol u should check the valves no matter what

 

[joshuafrazier]

my mechanic suggested i do a compression check, if it was good the valves are fine, if not.....

 

[Kgibson]

ummm...a compression test will not tell u what the tolerances/lash of the valves are

 

[Blaner]

just whip the cam covers off and check the shim clearance with a feeler gauge. nobody on here will know the specs off hand so so i still suggest you find a manual online!

 

[Drifz1]

check clearences ,and blaner said about the keeping the slide open , i never heard of it but theres a idle adjuster on the top of the carb which you just turn to change the height of the slide

 

[pittboss45]

The backfire can be caused from a number of things.
1, the exhaust system has leaks in it.
2, these are prone to have the coil pack crack
3, jetting
4, valves....004-.006 intake and .006-.008 on the exhaust.
5, a bad port job

 

[joshuafrazier]

The guy said he just had a new cam chain put in. The guy that did the work was from a yamaha dealer. The exhaust is missing the piece for it to slip on and also has different screws holding it in to the head. My dad and I are going to do the simple stuff first, then go from there. Does anyone know where to get a fan that has a switch so I can turn it on when I want it on. Thanks everyone! I'll get it all checked out.

 

[joshuafrazier]

The first day we looked at it, it started right up, and idled for about 5 min then shut off.

 

[Blaner]

Accelerator Pump Settings - Yamaha YFZ450 Forum : YFZ450, YFZ450R, YFZ450X Forums

another thing on the timing front, my brother once set his cam timing one tooth out on the exhaust side, now moving it one tooth one way sets it at the YZ exzaust timing but going the other way makes it real bad! he went the wrong way and wont start, when it did it wouldnt idle, a push start resulted the loudest backfire i have ever heard, the guy who was pushing was deaf in one ear for a few days!

if the guy had the timing chain off, chances are the problem is with timing

 

[BugsBunny]

I:I Everyone has given ya things to look at - I hate these bikes you buy & need to start going over every setting to verify what previous owners toyed with.

Replaced every singe wire, switch & stator on a Raptor 660 a year ago - in the end the flywheel was bad from a previous owner using a jaw type puller on it.

Find a shop manual for the bike - use it
Compression check
Check the timing chain make sure its dead on
Check the valve adjustment - should be a cold setting & maybe a running setting - RTFB

once those are known good you can start looking for air leaks or carb adjustments causing the lean condition.

The raptor described above had that MASSIVE pop in the EX & was hard to or a no start type situation, who would of guessed a flywheel?

Good luck with that.

 

[joshuafrazier]

The backfire wasn't loud actually. I'll get back to you guys on what I do and what works

 

[Drifz1]

never leave a 04-05 yfz idling for long unless it has the oil mod done !unless you wanna blow it up lol

 

[Blaner]

^^^agreed! its easy to put the cam pullies on the wrong way cause they have 2 markings on each, you need to know which to use. chances are, thats what wrong

 

[Drifz1]

^^the lobes should be pointing downwards at TDC.......you also cant do a compression test as theres a de-compression valve