Honda Twins banner
1 - 15 of 15 Posts

·
Premium Member
Joined
·
239 Posts
Discussion Starter · #1 ·
'74 CB450
After rebuild, adjusted valves, set timming static verified with strobe, sync'd carbs, idle's great at 1000rpm, K&N pods, baffle in pipes (VW tips), new plugs.
In neutral it will run all the way up to 9500rpm's no problem and come right back to ilde quick.
When I have it on the road my right cylinder cuts out at 5000rps in every gear.
Where do I start...
Hope I have provided ample info, if not please ask.
Just wondering where to start my trouble shooting.

Mat
 

·
Registered
Joined
·
3,926 Posts
Would cutting out under load suggest an advance mechanism problem?? Maybe a worn out spring?? Just thinking out loud...


GB :mrgreen:
 

·
Premium Member
Joined
·
239 Posts
Discussion Starter · #3 ·
Hmmm... Thanks GB, Thought a little about that, It advances as it should with a strobe light on it and visually the advancer unit looks to be in good shape (I failed to mention all this in my first post) I guess the only way to rule that out would be to replace it?

By the way, my first and only plug reading was good... mabey I'll do another just to make sure.
 

·
Sensei
Joined
·
27,180 Posts
One possibility........
Are the point gaps within spec?......IF the right gap is too large, the points will not make adequate contact when at high revs, but will run reasonably OK at lower revs....
The cure is to check, adjust gaps and retime as/if necessary
 

·
Premium Member
Joined
·
239 Posts
Discussion Starter · #5 ·
66Sprint, I think your on to somthing, I was having a hard time geting the gaps close to the same on both sides and still have it timed properly. I followed tbmusics instructions and did it several times but that could very well be it. I'll let you know what happens. Thanks!
 

·
Registered
Joined
·
608 Posts
check float levels, fuel flow thru both feeds of the petcock, could be running out of gas at high rpms
 

·
Sensei
Joined
·
27,180 Posts
Gaps DO NOT have to be the same...Just within specs ...Usually they ARE different.....Gap the left side...the right side ends up wherever, but MUST be within specs...........
 

·
Registered
Joined
·
30 Posts
I had a similar problem at one stage that turned out to be a dodgy coil. Seemed fine at idle but not under load. Just a thought.
 

·
Registered
Joined
·
19 Posts
Both of my 450s did that when i put them on the road. New condensers worked like majic. Cheers Peter
 

·
Premium Member
Joined
·
239 Posts
Discussion Starter · #11 ·
Well, first I replaced the points and re-timed, no change.
Next I replaced the condenser, no change.
Then I rebuilt the carb (again), now it cuts out at 4000rpm...
So I'm guessing it has somthing to do with the carb, since that is the only thing that made any change even tho it was a negative one.?.?.
Should I rebuild the carb yet again, or ?.?.?

(Edit) - Just noticed a slight exhaust leak at the right header/flange. One of the studs on the head where the 'doughnut' connects is pulling out of the head.
Could that be the culprate?
Also, I am still waiting on my new coils...

Mat
 

·
Premium Member
Joined
·
239 Posts
Discussion Starter · #12 ·
So I removed those damn K&N filters I thought looked so cool, and went for a ride around the block without any filters and she ran great. No hesitation, bogging, backfire, nothin... Strong on both sides all the way up to 9000rpm. :p

I'm not a big fan of the unifoam look so I am going to try to find a diffrent filter but will probably have to run uni's untill I find somthing I like. :|

What do you guys think about velosity stacks? :?

Now I want to know why the K&N filter did'nt cause the left cylinder any problems but messed with the right side so bad... Any thoughts? :?:
 

·
Registered
Joined
·
6,495 Posts
Whenever it's the right side only that acts up on a 450, I immediately put timing at the top of my "suspicious" list.

They're pretty sensitive to dwell, which relates to the point gap. It's critical to end up with the point gaps close to the same on both sides. This may take a number of tries to get right.........
 

·
Premium Member
Joined
·
239 Posts
Discussion Starter · #14 ·
Thanks man,
This is what I got told when I said I was having trouble getting the gaps close to the same earlier in the thread...
66Sprint said:
Gaps DO NOT have to be the same...Just within specs ...Usually they ARE different.....Gap the left side...the right side ends up wherever, but MUST be within specs...........
Got new points did static timming... I will put the strobe on it, and fine tune the gaps.
I am just glad I figured out the K&N filters were the problem, it's weird that it only affects the right side...

Without any filters on, it runs great, right and left.
With unoiled K&Ns on, right side cuts out @ 5000rpms, left side runs fine.
With oiled K&Ns on, right side cuts out @ 3000rpms and backfires occasionaly, left side runs fine.

Can't hurt to check the timming again, but I am sure I need to find a new solution for filters.
 

·
Registered
Joined
·
165 Posts
With one set of points timed by the plate, and the other by modifying the gap, I don't think it's unusual for the resulting gaps to be a bit different... Mine are .012 and .015 and it runs fine.............Took several tries to get it though....
 
1 - 15 of 15 Posts
Top