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[crfsonly]

Welcome to CRF's Only! Congrats on your new ride and to the world of modern 4-stroke dirt bikes.

First, don't be intimidated by these motors. Get the Honda Service manual and/or the Clymer manual. If you've wrenched your 2-strokes you can quickly learn to wrench these 4-strokes.

Second, the first thing to learn is to do is checking valve clearance. Here's a link to a How-To that will show you step by step how to do this:

http://crfsonly.com/howto/450r/valve-ch ... -check.php

Do this now so you know if your valve clearance is the primary contributing factor for your starting issues. If the valve clearances are within spec then report back and we'll go to the next place to look...the carb.

Third, if your valves are tight you'll need to have the valve seats professionally CNC cut and new valves and springs installed. We offer these services and valves. They things to look for when getting this work done is the following: 1. Seats cut with CNC equipment. 2. New valves installed with new springs, retainers and cotters (keepers). Make sure the springs and retainers are made by the manufacturer of the valves for the valves being installed. Some will spec cheap foreign valve springs and reuse your retainers and cotters. This is setting you up for very expensive engine damage when you drop a valve due to poor quality parts or fatigued used parts. Others will not recut the seats or will use hand cutting tools. Either will significantly reduce the longevity of the new valves.

Fourth, we use Kibblewhite stainless steel valves for durability. Coupled with our CNC valve seat work and the KW valve spring package the KW stainless valves provide maximum possible valve durability. This set up will provide you at least three times the valve durability of the stock titanium intake valves. You essentially would pull you head and ship it to us for this service and these valves. Here's a link to this service:

http://www.crfsonly.com/catalog/product ... ts_id/3974

Fifth, while you have the head off, inspect the piston. These piston have short skirts and essentially rock in the cylinder. The skirts wear and if worn enough will damage the cylinder and or rotate under power and cause all kinds of expensive damage. If the piston is not in spec replace it along with the pin, circlips, and rings. We stock several piston kits for this purpose.

Any questions you have, products or services you need just ask. Again, welcome and congrats on your new ride. You are going to really love how it runs!

Ken

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[crfsonly]

with the right starting procedure a well running CRF will start 1-2 kicks every time. cold start procedure. choke on. 3 quick whacks of the throttle. load up the kick starter. quick and deliberate kick. keep your hand off the throttle when kicking. put it on the master cylinder. any throtle will lean it out which cold motors don't like.

check valve clearance.

ken

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[crfsonly]

sorry to hear this news! these really are very simple machines to maintain and repair and you have a great support group here if you need it.

ken

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[scotsy]

I had similar symptons when i bought my 450r about a month ago and despite me doing the correct checks i was led astray by some clues that caused me to be looking in the wrong place for the answer

http://www.crfsonly.com/forum/viewtopic ... sc&start=0

This is my 3rd 450 and I immediatly checked cam timing and valve clearances, they were perfect so i started to suspect the carb (i had a good spark but fitted a new plug anyway)the jets were too large but the fuel screw had no spring or washer on it so when these came in the post i was raring to try again!!

I'm 58 and not very fit and soon got fed up trying to start it when everything seemed to be right so i bought a top-end gasket set and during the holidays i tore into it.

Even though I had .011" exhaust valve clearance it turned out to be leaking EXHAUST valves due to some bad shop work when they did the SS inlet conversion.

The carboned up state of the EX valves and ports and a simple 'pour petrol down the ports test 'proved that i was losing my compression down the exhaust valve seats when trying to start it.

So it had the symptons of tight INLET valves but they were perfect and the totally ignored exhausts were the actual culprits

Ian

[crfsonly]

if you are having to adjust valves and then i fires but quickly goes back to not starting then you need to replace your valves and have a valve job. if you are saying they did that service and told you it's in tip top shape and still won't start shame on them. tip top shape is 1-2 kicks starting cold or hot.

[124]

On the flipside, the 08 450' is the probably the best overall bike and is very desirable. Although, getting long in the tooth a bit, you should get good money for it.

We can get it running though.

the dealer says it's "good to go"...

...but it won't start?

First advise - don't go to that dealer for service ever again.

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[crfsonly]

probably after about 4 hours of riding time it become more difficult to start, taking about 20 or 30 kicks, .... then it got to where it would start when it wanted to, now it wont start at all..... its now backfiring again when i try to start it, like it did to start with before i had the valves shimmed.

classic signs of a "shim and sell". meaning the valves were bad, previous owner shimmed them to get clearance and sold it. when the titanium intake valves tighten you can shim them however you will only get a few more engine hours out of them before they tighten again. check your valve clearance. very good chance of them being tight. if that is the case, i recommend sending the head into us for our CNC performance valve job with Kibblewhite Stainless valves. these will last at least three times the stock valves and will be extremely stable.

once you get this bike running as designed you'll love it. in fact, if i were a betting man i'd bet you'll be selling that new YZ in no time.

[124]

As usual, Ken is talking sense. Sounds like once the head is squared away, all will be well.

Enjoy the YZ in the meantime. Riding is good for the soul!

[Dirtclod]

I've been kick starting bikes for over 50 years each bike is a little different. 450 R's each have their own little quirks to start. What usually works for the R's kick the bike through a few times with no choke and don't pump the gas. Then pull the choke, pump the throttle once wide open, take your hand off the throttle, then kick it again. If it's real cold adjust your idle up a tad. Good luck.

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