First post and engine problems

[pstarnes]

I have a ‘71 CL450 that has been giving me trouble lately. First and second gear are basically fine, unless you get over 5,000 rpm or so... and once you’re in 3rd gear, about 1/2 way through the rpm range, it starts cutting out and sputtering. I know the left cylinder isn’t firing at that point  because I can manipulate the throttle on the left carb and there is no rpm response. I know i’m getting fuel, air and spark because i just overhauled the carbs, the air filters are brand new and I just changed the spark plugs. What could be the issue? Points? Ignition coil? I’m really lost at this point.

thanks

Phil

[TOOLS1]

Since you had the carbs off and rebuilt I would start by checking for vacuum leaks. I use starting fluid to do this. With the engine running, spray around the rubber boots between the carbs and head and around the carbs themselves. If the engine RPM changes you have found the leak. Also, these carbs are known to leak around the throttle shafts so be sure to check there. When you rebuilt the carbs did you use an aftermarket rebuild kit? If you did take all those parts and put the brass Honda parts back in and go to your local Honda dealer and get all the new O-rings from them. They have them! I have had parts in rebuild kits drive me crazy because they are not made to the correct dimensions like the Honda parts. Another thing to check would be the vent in the gas cap. If it starts acting up just open the cap and see if it runs better. Oh, and does it run better with the choke on?
TOOLS

[pstarnes]

I can check the boots. Hopefully that is it. I know it isn't the carbs because I took them both off and switched them. I put the left on the right and the right on the left, and the left carb (the one I thought I was having trouble with) worked like normal on the right cylinder. That was maybe not the best way to do it, but it worked. I will check to see if its a vacuum leak and get back with y'all. Thanks for all the help. 

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From: TOOLS1 [via Vintage and Classic Honda's] <ml+[hidden email]>
Sent: Thursday, September 13, 2018 8:28:44 PM
To: Phillip Starnes
Subject: Re: First post and engine problems

 

Since you had the carbs off and rebuilt I would start by checking for vacuum leaks. I use starting fluid to do this. With the engine running, spray around the rubber boots between the carbs and head and around the carbs themselves. If the engine RPM changes you have found the leak. Also, these carbs are known to leak around the throttle shafts so be sure to check there. When you rebuilt the carbs did you use an aftermarket rebuild kit? If you did take all those parts and put the brass Honda parts back in and go to your local Honda dealer and get all the new O-rings from them. They have them! I have had parts in rebuild kits drive me crazy because they are not made to the correct dimensions like the Honda parts. Another thing to check would be the vent in the gas cap. If it starts acting up just open the cap and see if it runs better. Oh, and does it run better with the choke on?
TOOLS

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NAML

[TOOLS1]

Swapping the carbs like that was great thinking. I do not know about that model bike, but does it have two fuel lines coming off the petcock? If so have you checked for fuel flow on both of them or, have you loosened the float bowl drain screw to see if gas ran out on each carb? Have you tried giving the left side a shot of starting fluid to see if it catches? After these checks, we will need to move to ignition.
TOOLS

[pstarnes]

Yes it does have 2 fuel lines coming from the petcock. I can recheck that to make sure it is getting fuel correctly to the carb... It might be rubbing a little on the rear of the engine or it could be kinked. Thanks

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From: TOOLS1 [via Vintage and Classic Honda's] <ml+[hidden email]>
Sent: Thursday, September 13, 2018 11:35:24 PM
To: Phillip Starnes
Subject: Re: First post and engine problems

 

Swapping the carbs like that was great thinking. I do not know about that model bike, but does it have two fuel lines coming off the petcock? If so have you checked for fuel flow on both of them or, have you loosened the float bowl drain screw to see if gas ran out on each carb? Have you tried giving the left side a shot of starting fluid to see if it catches? After these checks, we will need to move to ignition.
TOOLS

---

If you reply to this email, your message will be added to the discussion below:

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NAML