Not Real Familiar with the CB750s ...

Posted by mespock on Aug 27, 2012; 10:27pm
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Not-Real-Familiar-with-the-CB750s-tp4028141.html

Need some help from someone who may know more about the 750K ... I have a 1979 750K with a 1980 750 Custom's engine. I purchase the 79 because it was in great shape but engine was so so ... found the 80 because the engine seemed to be in good shape but the body .. yuck ... LOL .. So after the the build and having the carbs sync..ed ... I've been becoming familiar with the bike.

Youtube Video

On Monday I went a a 125 mile ride ... I took my GL1200 and I let a friend take my 750K.  He said he had a hard time keeping up with me and said the bike dogged up hills.  Plus at 100 miles he had to go on to reserve.

On Friday filled the tank and took it out to see if it was his riding skills or the bike.   After warming it up for about 5 miles I took it up to 60 mph and then found as the the bike struggling to go over 60 mph.  Then up a hill it would really struggle.  This was all in 5th gear.  Next I went to play more with running at about 8000 rpms before shifting.  I could get pretty good response up to 4th gear but then in 5th not so well.   I took it up to 90 mph twice on the second time I blew my muffler off my right side. Enough that they separated at the joint.

I replaced the muffler and then put on about 20 more miles today bringing my miles to 70 since I filled it up on Friday.  I blew air through my muffler to see if there was anything plugging it.   Bike ran OK but still seemed a little restrictive.  When finished I filled the bike and then measured the mileage.  only 27 mpgs.

So .. I'm only getting about 25 to 30 mpg on my DOHC 750.   I'm not really sure how it should perform.  I have been told that I should be getting somewhere from 45 to 50 mpgs, and I expected it to be more responsive.

Also how should is perform in 5th gear?  On flat surfaces it runs great up to 60 but then levels off and will slowly climb ... 4th gear is very responsive.   Going up a hill there it takes everything to hold at 60 mph in 5th gear.  In 4th it climbs fine.

So any suggestions?