Topic: 73 honda 750 has no power under a load

[honda 750]

i just got bike running after 30 yrs in storage    had carbs all redone. bike starts up and has plenty of rpm at idle but when i took in down the road for test run . would only get about 5000 rpm and 55mph  on hiway   there was no top end power. any help will help

[ekpent]

Check the timing and advance mechanism. Do wet rag test to make sure all 4 cylinders are hitting well. Sure others will have lots more suggestions.  What set up are you running as far as pipes,filter etc.

[honda 750]

running all stock  filters and pipes     carbs were re jeted to 100

[Really?]

I there a reason why your jets are 100?  Altitude?  I think the 75/76 were 105's and prior may have even been 110/115/120. 

[Really?]

I found this link http://www.motorcycleproject.com/motorcycle/text/specs.html in the FAQ thread - http://forums.sohc4.net/index.php?topic=5410.0

None are at 100.

[honda 750]

thanks for the thread
     i rechecked slip on carbs and they are 120 jet

[Really?]

A good recommendation, if you have not done it yet, would be to do the 3K tune up that is in the downloadable manual.  It would be good to know what every part needing to be checked is right (i.e. timing chain adjustment, valve adjustment, points/plate adjustment and condition...).

Since you said that the filters and pipes are stock, jetting at what it is supposed to be per the carb model number should be a good place to start.

You can checked for air leaks on the front a rear boots of the carbs too. 

[andy750]

thanks for the thread
     i rechecked slip on carbs and they are 120 jet

If you are running all stock then 120 are too large for a 73 750 - check your plugs are they all dark and sooty? Drop to 110 or 105s or/and check the stamp on your carbs - 657? Then do a check of which main jets were stock for your carb - I dont recall off hand but Hondaman posted extensively on this so do a quick search. Also verify the main jets/emulsion tubs are actually clean - did you do it yourself or someone do it for you?

I had an issue like yours once and it turned out to be a faulty condensor. But check the fuel pathway first.

[honda 750]

i had carbs done by old school carbs

[Johnie]

Just to rule it out...by any chance did you do a compressoion check?

[Duke McDukiedook]

Points ignition?
You sure all cylinders are firing and the header pipes are the same temp?

[honda 750]

compression is good on all4 cylinders   130-145     spark on all cylinders    did find #4 cylinder not getting gas  plug is like bran new no sign of firing at all    so i will look at that carb to see what problem is

[Old Scrambler]

Is it a new air-filter? 

[ekpent]

compression is good on all4 cylinders   130-145     spark on all cylinders    did find #4 cylinder not getting gas  plug is like bran new no sign of firing at all    so i will look at that carb to see what problem is

Might be as simple as the float or needle being stuck or bound up. Wiggle it around a little,put the bowl back on and give it a try. Love those clips instead of screws. By turning on the petcock with the bowl off you can also confirm you are getting a good flow.