Jump to content
Sign in to follow this  

Help! Can't get 07 CRF450R started!

Recommended Posts

Hey guys, I am new here. I bought an 07 Crf450r a while back. It was always a little harder to get started and made some engine noise. The noise almost sounded like the piston slapping around. This is a used bike, and it doesnt sound like the previous owner ever had the top end changed. I pulled the valve cover off and reshimmed the valves, thinking maybe that would help me get it started easier and maybe eliminate some noise. The valves were only .001 out of the recommended specs so I didn't feel they were horrible. I shimmed them to be right on.

After putting bike back together, I tried starting it. I couldnt get it started without removing the air filter. I thought maybe it was because it was so cold out, or I had too much oil on my filter. Once I cleaned my filter and got it running, I didnt have any problems after starting it a few times throughout the next few days. The engine noise was still present. About a month ago, I went to start it, and I ended up kicking it about 50 times and it finally started. Rode it around for a while, stopping/starting it multiple times.

The other day I went to start it and had no luck. I took the air filter off, thinking maybe that would help. I tried push starting it too and that didn't work. I squirted gas directly into cylinder to bypass any potential carburetor problems. No luck. I bought a new plug, even though my old one was sparking when I grounded it to the engine and kicked it over. I did a compression test and my compression was between 48-50 psi. I read that 50-65 psi is good for these when using the auto decompressor. I checked my valve clearances and that all looks good. I did not check my decompressor clearance as I am not sure how to do that? At TDC my timing marks are perfect, as well.

Does anybody have any insight for me on where to go next or what to try? Would you be concerned about my compression being too low? I am thinking maybe the top end needs to be replaced but I was hoping to get lower compression results back.

Thanks in advance.

Share this post


Link to post
Share on other sites

If you held the throttle wide open when you did the compression check it should have been closer to 70-80 psi. When it was running, did it backfire on deceleration?

And the decompressor lash isn't adjustable on that year bike. So you dont have to worry about it Unless you got the gear onto the cam without the pin being inside the weight and the decompressor is engaged all the time.

It takes about 70 psi to create any kind of combustion, so if youre not there, it wont start. For what its worth, these engines are noisey as hell. Even when they're right they make quite a bit of racket.

Share this post


Link to post
Share on other sites

Valves. The face of them has eroded and they are no longer sealing correctly

While possible, if you can get the lash set, they'll usually seal enough and well enough to run. Ive seen valves come out of a running engine that were worn to a razor's edge around the margin.

I think he's got something additional going on.

Share this post


Link to post
Share on other sites

Agree, just rebuilt mine, new everything, and glad I did If I hadn't I would be nervous right now...very noisy motors.

Share this post


Link to post
Share on other sites

Thanks for the input guys. I have owned a few different 4 stroke bikes in the past few years, none of which were hondas, and have never heard any "regular" engine noise this loud and distinct. The bike has ran a few times since I shimmed my valves, so I am assuming the decompressor pin is installed correctly. Everything looked good when I put it back together. I did not have any backfire on decel before either. Once the bike was running, other than the engine noise, it ran good and felt like it had all of the power that it should.

Share this post


Link to post
Share on other sites

The best way to deal with the noise issue is post a video.

This kind of sounds like a problem I had with my 250X. It would run fine and then quit out of nowhere and be really hard to start. Turned out being some dirt in the carb.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...