Topic: 400/4 Carb issue

[denward17]

How did you adjust the floats, by pushing down all the way ?
Or take the measurement with the float as high as it would go?

[MDW]

denward17: I had the carbs at a slight angle so the tag was just touching the needle. I set them to be 21 mm from the highest part of the float (they were pretty much level so there wasn't really a higher place) to the rim where the bowl connects.


I rigged up a test to check if the needle valves are working. And they appear to work fine when I manually close them with the floats. That would seem to take us back to the float height adjustment (unless all four overflow are leaking). As mentioned, I don't think I messed up setting them at 21mm. I assume the 21 mm is valid for all 400/4s. Does it make sense to set them so they cut off earlier? Guess not.

 

[MDW]

Last post for today. I put the bowls back on and ran gas through the carbs. I gave all bowls a good heavy  tap with a rubber screwdriver. Nothing came out of the overflow. I emptied the bowls and ran gas trough again. 3 overflows leaked. Gave them a few more whacks and ran the gas and no leaks. I am going to call that a success for today!

[denward17]

Without reading through thread again, are you still using the original float seat and needle?

[MDW]

Yes I am. They looked in really good shape. The needle spring movement felt the same as the new kit I bought.

[MDW]

Some good news. My carb leaking issue seems to be fixed. However, the engine, although running better is still a way off being right. It will run at high revs (guessing 4-5K - I don't have the rev counter fitted yet) and rev higher on the throttle before returning to the high idle. It then seems to get rougher and eventually stops after a few minutes. I think the carbs are adjusted about right. I am now checking the basics like plug gaps, points gap, timing. I wanted to check the cam chain adjustment but just read that for the 400 (unlike other 4 cylinder Hondas from the 70's) that needs to be done while the engine is running at 1200 rpm. Has anyone made the adjustment without the engine running? As my idle is too high, it would prevent me adjusting it.

[scottly]

Check that the ignition advance is returning to the F mark at idle. Weak springs can allow the timing to stay advanced, speeding the idle up.

http://forums.sohc4.net/index.php/topic,194888.25.html

[MDW]

Thanks. Not sure how to do that but will look for it on YouTube. Do you need a strobe light?

[scottly]

Yes, you need a strobe, but you can try slowing the engine down to see if the idle drops until the next time you rev the engine.

[bryanj]

Yes you can adjust it without the engine running IF the tensioner horseshoe is not siezed.
1 undo the adjuster locknut
2 loosen the adjuster bolt
3 put pressure on the kickstart until the engine is just about to turn then whilst holding the pressure on kickstart do up the lock nolt then nut.

If you do this on a hot engine you will burn at least one finger/hand

[MDW]

Thanks!

[Ozzybud]

Are your slides still open 1/8 of an inch at the bottom stop?. We need to get this fixed first. All of your synchronization adjusters need to be lowered. Is the idle adjustment screw even touching the stop?

[MDW]

I had the slides at 1/8 or 3mm. This afternoon I  started to lower them more and all of a sudden the engine started to run way better. They are now pretty much how they were when I bought the bike(1-3 closed, slight gap on #4)  but the PO was running pods and I have gone back to the original air box. The idle is touching the stop but not by much. Some fine tuning left still.

[Ozzybud]

Pods will have nothing to do with slide position and synchronization. The 4 synchronization screws need to be adjusted so the slides will freely close all the way
 Then the idle adjustment can come into play.

[MDW]

Hoping to borrow a vacuum gauge next weekend