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Discussion Starter · #1 ·
Happy Monday everyone!

After a couple of weeks of casually working on my new-to-me 1983 CM450A I finally took my first ride around town yesterday afternoon had a blast!

This bike was a craigslist "worked when parked but lost the keys" gamble that I bought for next to nothing knowing that it could well turn into a major headache depending on how much the seller was lying... luckily I think I found the one honest guy on craigslist still left out there and really haven't had much trouble getting the bike back in order. I ordered new keys, replaced all the cables, plugs, fuel lines, oil, filter, fuel filter, and the battery. I tore down and chem-dipped the carbs, replaced both air cutoff valves, accelerator pump, and throttle spring and grip tube. Initially, once I got the new keys, the bike would start right up but was stuck at full throttle. Replacing the cables fixed that but then it did the opposite... would idle fine but die with any throttle. Rebuilding the carbs and/or replacing the air cutoff valves fixed that.

After the first round the block ride yesterday I did my best to dial the carbs in and got the mixture and idle set well enough to let me take a good 40 minute or so tour around town without any trouble. Definitely needs some more careful tuning but that'll come soon enough.

This is my first time riding a Hondamatic bike so I'm wondering about how it is supposed to behave when at idle... It seems that when I'm stopped at a light and have it in gear it needs the idle to be set higher than it would in neutral to keep from stalling. Makes sense since there's load on the engine when its in gear and stopped, but it feels like when it is idling high enough to not stall it pulls much harder than I expected... that is, if I'm on a level street and am not holding the brake it will creep forward while just at idle. Obviously I can stop that by shifting down to neutral when at lights, but I'd prefer not to do that and keep it in gear so I can more easily escape if I'm about to be rear-ended or side swiped. Lowering the idle to the point where it doesn't pull puts it in danger of stalling. I'm nervous that sitting at high idle like that while holding the break is going to put too much wear on the torque converter or a friction plate somewhere or some such...
So is this just life with a Hondamatic, or is this something that can be evened out with better tuning?

This is also the first time I've ridden an air-cooled Honda twin and it felt quite a bit warmer around and under my knees than other air cooled bikes that I've been on in the past. Kinda smelled hot as well... is that normal for these motors, or should I be concerned that its running too hot? I'm going to measure it at temp this evening with an IR contactless thermometer, what temp range should I be expecting?

Finally, the valves seemed pretty loud once it got up to temp. How normal is that? I'm going to do a valve clearance adjustment as soon as I get a chance, but I don't want to end up trying to fix non-problems if I can avoid it...



Thanks again for the help and advice I've gotten along the way with this bike... I live right downtown in a major east coast US city with no access to a garage so I have to do all my work right on the sidewalk. I don't have the luxury of being able to work on more than one major thing at a time, I'm limited by weather and daylight, and have to make sure everything is put back together when I'm finished each time so having this forum to read up and work out problems ahead of time is a huge help!

Also huge thanks to the engineers at Honda for designing a bike that is so easy to work on... 1 bolt and the tank is off. 2 screws, 1 hose, and 3 cables and the carbs are out as well. When I'm riding I can easily reach down to adjust the idle or mixture screws, there's only 1 fuel petcock to worry about, and no vacuum lines to leak and screw everything up. I'm still used to my Suzuki GS500 which is a nightmare to get down to the carbs, has 2 separate fuel petcocks, multiple fuel lines, and a mess of vacuum hoses that are always causing problems. I have to pull the carbs to adjust anything other than idle speed which makes it impossible to adjust and tune things on the fly. When it runs well its great but it takes an entire afternoon to do just about any work on it and is so frustrating...

-Joe
 

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Welcome to Hondamaticing Joe,

From my own experience of a 400 Hondamatic it does sound like you have a problem with the idling. Creeping at idle should be almost imperceptible and engine revs should be nearly the same whether in gear or neutral. As you rightly say there is more drag on the engine when in gear and Honda have fitted a switch in the gearbox to tell the ignition box to alter the timing when in gear to compensate for this.
In my experience anyway, this means reliable idling in neutral. A good clonk when engaging gear but unchanged revs and an engine that is unstallable whatever I do with the throttle.

I'm sure much more and better informed advice will be forthcoming :)
 

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Welcome
 

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Discussion Starter · #4 ·
Thanks for the clarification... I was willing to live with it if that's just how these bikes run, but that's good to know that it isn't normal so I can work on fixing that.

I'm hoping that once I get the valves back into spec that I'll be able to better dial in the mixture and idle settings. For what its worth, I rode the bike in to work this morning and it was idling a bit better... at least it didn't seem to be pulling as much when I was stopped. I was a bit nervous taking it through downtown rush hour traffic for the first time in case it stalled on me at a red light but the whole trip in was a breeze and the ease of negotiating the stop and go traffic and hills that define my commute was a great way to start the day.
...now I just need to get out of the habit of kicking it down into neutral when starting off from a light :)

-Joe
 

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It sounds like there's some fine tuning needed. Have the carbs been sync'd yet? Idle speed really needs to be set with a tach. Do you have the FSM? it explains the ignition and idle systems for the A model.
 

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Hi Joe. First of all I have not worked on a 450a but I dont think there is a lot of difference between the 450 and the 400s. LDR is right you need to sinc the carbs and pick up a FSM. there is no tach on these bikes so pick up a pulse tach. Mine is a Smart Tach+ Ta100. When in neutral the motor should idle around 1250+- 100 rpm. When put into gear the idle stabilizing circuit thru the CDI box raise the timing from 7.5 degrees to 15 degrees and the idle should be 2000 +_- 500. Mine is set at 1800.

There is a sticky in the 400 elec section that should help you a lot.

I hope this helps.

Bill
 
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