450F Honda crf 450 Dosent start....

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ossagp

Darn, why fight the idea of checking the valve clearances and at least eleminate that, the most common cause of hard starting on the newer 4 strokes?

If you get your largest clearance anywhere other than when the crankshaft is on TDC then you know you jumped timing on the cam/valves.
 
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timoyz

timoyz

And it being a just bought 03 Honda, I see major red flags. When valves are old, and have been adjusted many times, each concurrent adjustment will last less, and less time. So bad, that it will only last 10, or 15 minutes when it gets to the end of it's service life. Sound familiar? Now for some more questions. Do you know the previous owner? Did he know the head was toast, and did a shim and sell? When was the last time the bike had a complete valve job? How many hours are on that valve job? When was the last valve clearance check? How many shim sizes were needed? How many times have each valve needed to be re-shimmed? Is re-shimmed even a real word?

Listen to the masses. If your carb is clean, and you have a spark, do a valve job before one of those tuliped valves snap, and you have to add a lot more parts to your list.
 
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Mihylo33

Mihylo33

timoyz:
And it being a just bought 03 Honda, I see major red flags. When valves are old, and have been adjusted many times, each concurrent adjustment will last less, and less time. So bad, that it will only last 10, or 15 minutes when it gets to the end of it's service life. Sound familiar? Now for some more questions. Do you know the previous owner? Did he know the head was toast, and did a shim and sell? When was the last time the bike had a complete valve job? How many hours are on that valve job? When was the last valve clearance check? How many shim sizes were needed? How many times have each valve needed to be re-shimmed? Is re-shimmed even a real word?

Listen to the masses. If your carb is clean, and you have a spark, do a valve job before one of those tuliped valves snap, and you have to add a lot more parts to your list.
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So you're still thinking valves???
I would concur....:stirthepot:
 
timoyz

timoyz

Eliaschr12:
Hello there.

I live in Sweden and I just bought a Honda crf 450 -03, It was runing great until I was going out in the forest-- Low Rpm and low gear and it easily died and realy dident have the power to run there, I really needed to go hard on the clutch. I took a look on the camchain and everything was okej, I was driving it for about another day, when it suddenly died and dident want to start more. So I took a look at the sparkplug and it was bright blue and good. But still it dident want to start. The valves looked decent when I measured them

When Im trying to kick start the bike it dosent feel that hard like it used to a little easier to kick like no compreassion. I tried with Start gas but it dident even do nothing. So I took another look at the spark I saw the spark was coming and going but I shaked around the cabels and fixed it up tight, and it was steady, spark everytime I kicked. I also checked the stator and was on 18.99Ohm when I meassured with my muiltimeter it is supose to between 9-25. But still no look nothing with startgas or fuel. What do you think is the problem. it makes me frusterated beacuse I cant seem to find the problem. Oh yeah its rebuilt so it haves light and stuff atm. Please help and thanks for answering.



1 Camchain -ok

2 Stator what I belive is ok

3 It doesnt even do nothing with startgas

4 To easy to kick

I have no clue what to do.
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How did you verify the cam chain was okay? Did it "look" okay, or was it measured with a actual instrument?

Eliaschr12:
Are you sure about that? I have compression but the shit aint start =/ When you are guessing its the Valves, in that case why? :D
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You can still have compression with valve clearances too tight.

Mihylo33:
So you're still thinking valves???
I would concur....:stirthepot:
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Since there is no :ride: in this thread, it has to be the valves.:smirk:
 
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Eliaschr12

timoyz:
How did you verify the cam chain was okay? Did it "look" okay, or was it measured with a actual instrument?


I cheacked it by the marks on the chain and like that " youtube video" :/ . I have accutaly not been looking at the timming on the spark. And I have no Idea if the valves where old, But I have name and number so I will call him and ask.
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Mihylo33

Mihylo33

timoyz:
How did you verify the cam chain was okay? Did it "look" okay, or was it measured with a actual instrument?



You can still have compression with valve clearances too tight.


Since there is no :ride: in this thread, it has to be the valves.:smirk:
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Love my :ride: but since thee are none here it must be valves....


@Eliaschr12 ... @timoyz probably has more 4T build experience than anyone else on this forum. Honda 450's love to eat valves so I would get a service manual and really dig into this thing before bouncing it off the rev limiter when it finally does start. good luck
 
timoyz

timoyz

Cam chains can stretch, there's usually a length limit for ten links. If you do a rebuild, chains are cheap, do yourself a favor and replace it regardless.
 
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ossagp

Eli. The previous owner answering your question of how old the valves are is not actually going to make your bike start. Eleminating the causes that are keeping it from starting is the way to go, no matter where you go, and what the previous owner says.

CRF's with their mismatched for long life materials in the head are known for fast wear, particularly the intakes. 250 and 450 alike. First thing to do is make sure the clearances are right and that the timing of them is right too. It is EASY to do. Fast, cheap.
 
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