Go Back   Motorcycle Forum > Manufacturer Forums > Honda

Reply
 
Thread Tools
Old 04-24-2009, 03:50 PM   #1
numb3r
Registered Member
 
Join Date: Apr 2009
Posts: 5
Default 72 CB350 loses power on hiway. Help!

Hi everyone,

I'm new here but was wondering what your thoughts are on this.

I have a 72 CB350. The problem is that whenever I bring the bike on to the freeway it begins to lose power and die. After the bike dies, it will take around 10 minutes before it will startup again. It takes about 1 mile at hiway speeds for the bike to lose power and die. I've successfully ridden it all over the back roads, really pushing it through all the gears. I can get it up to 60+mph no problem on these side roads but I can't maintain that speed for long, as all the roads around me are curvey with stop signs (live just outside San Francisco).

What I've done to the bike so far:

- Carbs fully cleaned
- Gas tank flushed and cleaned
- Fuel pet****/nozzle cleaned/inspected
- New fuel hoses with clear filters
- New condensors

I've researched all over and to the best of my knowledge, and from what I've repaired/replaced so far, my next guess is the ignition coils. I replaced the condensors yesterday, and took the bike out for a good 10 mile jaunt through the hills... it ran great. I thought the problem was fixed, so I jumped onto the hiway today, and after just 1 mile DOWNHILL going a steady 55mph in 5th, the bike began to lose power and without feathering the throttle to give it power it died and I coasted for about 1/4mile until I was in a safe spot to wait and start it up again.

One of the reasons I've been playing with the fuel so much is that I've noticed after going on the hiway, there was air in the fuel filters. Gas was still going through the line but is that normal to not see the filter completely filled with gas? Here's how I have the filters hooked up: http://numb3rs.com/dump/fule_filter.jpg

Any ideas? Thanks much
numb3r is offline   Reply With Quote

Sponsored Links Remove Advertisements
Motorcycle Forum
Advertisement
Old 04-24-2009, 04:58 PM   #2
The_AirHawk
Founding Member
 
The_AirHawk's Avatar
 
Join Date: Jun 2007
Location: Leanin' Tower O' P-P-P-P-POWAAAAAAAAA!!!!
Posts: 11,491
Default

Those filters are OK, not the best in the world but OK. Have you tried running WITHOUT one, just to see if that's the problem? Definitely sounds like a fuel issue. But, it also has symptoms of overheating coils as well (namely the wait ~10 minutes thing).

After it dies did you try the old "crack the gas cap to listen for a vacuum-woosh-noise" to see if the cap-vent is plugged?

How about the carb vents - where are you venting those to, and is it possible the line is plugged, or that the tube is oriented where a "high speed" run creates a strange pressure-situation?

That's all I can think of off the top of my head. Cuddy, any ideas?
__________________
Parfois, on fait pas semblant
Sometimes, it's not pretend
Oderint Dum Metuant
Let them hate so long as they fear
политики предпочитают безоружных крестьян
Politicians Prefer Unarmed Peasants
Nothing to see here, Citizen. Move along now...
The_AirHawk is offline   Reply With Quote
Old 04-27-2009, 08:07 PM   #3
mscuddy
MODERATOR X

 
mscuddy's Avatar
 
Join Date: Jun 2007
Location: Next to my still checkin the temp.
Posts: 5,448
Default

Having owned several 350 twin Hondas it sounds like fuel starvaiton.
Those gas filters are crap, get some automotive type AC filters. That's what's causing the fuel starvation most likely, cheap in-line gas filters.

That, or the vent that's built into the flip-up gas cap is partially clogged.
__________________
A gun is a tool, Marian; no better or no worse than any other tool: an axe, a shovel or anything. A gun is as good or as bad as the man using it. Remember that.
mscuddy is offline   Reply With Quote
Old 04-29-2009, 06:29 PM   #4
numb3r
Registered Member
 
Join Date: Apr 2009
Posts: 5
Default

Thanks for the ideas guys. When the bike died the other day I popped open the gas lid but there was no wooshing sound or anything like that. However upon reading your posts, I inspected the underneath the gas cap and noticed the small vent. I rotated the round piece under the cap so the vent was facing towards the front wheel, and this actually has helped quite a bit. The bike seems to get a bit starved sometimes, but it hasn't quit on me since.

What's the best way to get in and clean out that vent properly? Should I just run wires through it? Leave it in some cleaner?

I'll also swap out those fuel filters, thanks for the help.
numb3r is offline   Reply With Quote
Old 04-30-2009, 02:31 AM   #5
blah blah
Registered Member
 
Join Date: Apr 2009
Posts: 10
Default

im losing power over 5000rpm, starter solenoid is corroded, but it feels like fuel supply issue....check your ignition system....jsut an idea
blah blah is offline   Reply With Quote
Old 04-30-2009, 09:39 AM   #6
The_AirHawk
Founding Member
 
The_AirHawk's Avatar
 
Join Date: Jun 2007
Location: Leanin' Tower O' P-P-P-P-POWAAAAAAAAA!!!!
Posts: 11,491
Default

Quote:
Originally Posted by numb3r View Post
What's the best way to get in and clean out that vent properly? Should I just run wires through it? Leave it in some cleaner?

I'll also swap out those fuel filters, thanks for the help.
Running a wire through the vent tube followed by a blast of compressed air should do it. Be cautious about using carb-cleaner around rubber parts - the solvents in it can cause some types of rubber to soften and swell-up.

Also, take care with the placement of the end of the vent tube - in certain instances, it's been documented that some bikes suffer from a "stumble" or "bog" when the carb was vented to a venturi-like low-pressure area of the bike's frame. Google "HawkGT Crosswind Stumble" for just one example.
__________________
Parfois, on fait pas semblant
Sometimes, it's not pretend
Oderint Dum Metuant
Let them hate so long as they fear
политики предпочитают безоружных крестьян
Politicians Prefer Unarmed Peasants
Nothing to see here, Citizen. Move along now...
The_AirHawk is offline   Reply With Quote
Reply


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off