Losing power at higher speeds

[Kain]

Hey folks!

I have a problem with my CB360, I seem to be losing power at higher speeds (around 40-50mph). I thought it might be carb related but someone suggested that it could be ignition? and that the contact plate can warp? Or could it be my advancer? Any help is greatly appreciated. I don't get out on the highway much but I'd love to be able to when the chance arises.

I replaced my points and had my timing done (by a pro) at the beginning of the season. I think the problem started AFTER the timing was done.

 

[joevirus563]

Hey folks!

I have a problem with my CB360, I seem to be losing power at higher speeds (around 40-50mph). I thought it might be carb related but someone suggested that it could be ignition? and that the contact plate can warp? Or could it be my advancer? Any help is greatly appreciated. I don't get out on the highway much but I'd love to be able to when the chance arises.

I replaced my points and had my timing done (by a pro) at the beginning of the season. I think the problem started AFTER the timing was done.

I'd say, carbs...

 

[pablohoney]

Yeah, sounds like a lean mixture, I'd check the plugs.

 

[Big R]

Could be a couple things actually. Is it at higher speeds or higher rpms as well? And what do the plugs look like?

How old are your coils? Any changes to the intake / exhaust? Timing is easy to check yourself - just follow whats in the manual. Most likely it isnt the spark advance - i think it kicks in around 1000 rpm and doesnt have a huge effect after that.

 

[Kain]

Sees like it's just higher speeds. I haven't pulled out my plugs yet. If they're fowled it would be mixture right? I don't know how old the coils are... they'd have to be at least 3 years as that's when I got the bike. I changed the exhaust at the beginning of this season before I had the timing done.

 

[Big R]

But you still have the original intake?

Do a plug chop first (procedure can be found by searching in case you don't know how). If they seem a nice hazy white, they are running lean and you need to bump up the mains (and possibly the needle) because of the exhaust.

If you look at the coils and they look original, replace them. Bad coils will fail to deliver spark at higher rpms, then when they get hot they will shut down completely for about 20 minutes. Even if yours aren't technically "bad", Dyna coils will make a huge difference

 

[Kain]

All I changed was the mufflers that's all but they are real short and have no baffling.

I'm looking at making a purchase at Dime City but Dyna coils seem a little expensive for me right now but would <a href="http://www.dimecitycycles.com/universal-12-volt-ignition-coil.html">THESE</a> work?

 

[rockcitycafe]

advance on a 360 starts at 1800 and i believe stops at 3000, was the guy a pro at old bikes? or just a "pro", the points system on the 350/360 was retarded at best, you've got to screw with the dwell on the right cylinder point to adjust its timing, if he wasn't familiar with that, you could be getting a very weak spark on one cylinder at higher rpm, you can also check where in the rpm band the problem is by starting out in 3rd gear down an empty street and give it full throttle, it should accelerate slow enough that you can really tell where it's flat, is it running hot or blowing smoke? if the mixture needs adjusting, that can really affect things

 

[Kain]

The guy doesn't deal only in old bikes. But he's always got old bikes in shop and he has a good rep. I'll check where in my RPM I'm going flat today. It's not blowing smoke. Being in the city and the hot summer though I'm not too sure if it's running hot or not cause it's been super hot the last few times I've been out riding.

Noob/Early Saturday morning question coming up. How do I tell if it's too hot?

 

[crazypj]

40~50 mph isn't high speed for 360, (unless your in second gear?)
I'm running points and original coils to 11,500~12,000 rpm, nothing wrong with them if they are in good condition.
They are 'self limiting and will cause missfire somewhere around 11,500 rpm due to points 'bounce'
Points springs go weak and coils burn if ignition was left on and points were closed.
Carb diaphragms split, pilot circuit in carbs is frequently blocked or partially blocked.
I would check points first (with timing light, stops flashing if you have problem)
Then check carbs.
The slides may not be lifting properly, particularly if needles have been shimmed (needles HAVE to move in slide)

 

[Kain]

Alright. Took the bike out for a little today and pulled the plugs and checked them out. They're covered in carbon so... too rich OR weak ignition system (so says Clymer). So I think I'll bite the bullet on ignition coils and new air filters.... just have to find some air filters that'll fit... :S

 

[crazypj]

David Silver Spares (London UK) has new air filters for CB360
Or, you can try cutting up automotive filter and gluing it into original side pieces

 

[iSack1L]

David Silver Spares (London UK) has new air filters for CB360
Or, you can try cutting up automotive filter and gluing it into original side pieces

PJ, have you had success with this method of cutting auto filters. Any glue recommendations for this method? I'd like to keep the original boxes, but they aren't looking the best. Cheers.

 

[KrashManhatten]

in my case, i have a 74 honda 360, and i loose power in the upper rpms because of weak battery, thus leading to a poor spark.

just some thing to keep in the back of your mind, check the battery, start, throw a tester on the + - of the battery, and check the volts, and then rev up and see if the juice goes up. and also do this with the lights on, and off. might be suprised.

 

[Kain]

Weak battery is DEFINITELY NOT my problem. I had charging issues at the start and installed a brand new reproduction stator two years ago and haven't had troubles since with weak or dying battery. Even running high beams all the time in the city I really recommend this as an upgrade to anyone having battery issues.

 

[crazypj]

PJ, have you had success with this method of cutting auto filters. Any glue recommendations for this method? I'd like to keep the original boxes, but they aren't looking the best. Cheers.

I've never done it but I supervised it being done on a 360.
Find filter same 'thickness' as Honda one
Used silicon gasket sealer as 'glue'
Cleaning up sideplates is hard part (although keeping everything lined up is also a bit difficult)

 

[andrew]

I've never done it but I supervised it being done on a 360.
Find filter same 'thickness' as Honda one
Used silicon gasket sealer as 'glue'
Cleaning up sideplates is hard part (although keeping everything lined up is also a bit difficult)

i tried the auto filter routine and it worked but i was always worried that the filter was too restrictive as its made for a car and not for a bike, which flows alot less air. (maybe im just weird) i ended up getting a sheet of uni filter foam and cutting strips to place in the filters. the good thing about this is you can get the course foam like i did and layer it up or take a layer off depending on aftermarket mufflers/rejetting/etc. just my 2 cents. heres a photo.

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