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Motorcycle Repair/Honda trail 90 1972


Just purchased a low mileage 1972 trail 90. Motor runs great, bike starts smoothly on first kick every time.
Trouble is after 15 minutes or so the bike loses all power and dies. Will not restart til it sits for 5min or more then dies more quickly next time. When I say dies I mean all power is gone. no headlamps etc.
Bike can sit overnight and I turn on key and headlamps will be at full brightness and is starts right up.
Ive only had it for a few days, is this something simple ? battery issue ? I'm no mechanic....pleas advise.
Thank you

Jon, first you have to be sure that you have a fully charged and load-tested battery in the bike. With only 6v available, it doesn't take much to drive it below normal voltage ranges and everything quits.

Your charging system could be an issue, but try a new battery first. There is a rectifier which could have been damaged over the years.   #6

It sounds like the battery is trying to recover overnight, but either the charging system isn't working or there are excessive load requirements on the bike. Check to see that the brake light is NOT ON when the bike is operating normally. There is probably a front and rear brake light switch on the machine, so either switch can either be stuck ON or damaged to where the light is staying ON all the time. If this happens, it will drag the battery down quickly.  #8  If the plunger in this switch is broken off, the brake light stays ON all the time.

The rear brake light switch has an adjustment on the switch which allows for it to be moved up and down to change how it operates.  #1

The engine ignition system is battery-operated, so must have a fully charged battery in place. Get a small 6v battery charger and have it available to keep the battery fully-charged if you don't ride it all the time.

Bill Silver

Motorcycle Repair

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Bill Silver


Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.


I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

VJMC (Vintage Japanese Motorcycle Club) of North America

VJMC newsletter, as editor for two years and as contributing editor currently.

3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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