early 70's Suzuki problem

Friend of mine has a 73 or 74 (or 75 or 76..) Suzuki road bike, not sure what size but under 400. He took it on a 70 mile trip (140 RT) the other day and halfway to his destination it started making an awful metallic clanking noise. He was far from any town so he had to keep going. he found that in 6th gear it sounded normal, but in all lower gears it made the horrible clanking. Surprisingly he finished the trip in its entirely, staying in 6th gear when at all possible.

Not many bike mechanics around here. Got any ideas? I haven't heard it yet myself but I'm going to try to get an audio clip

Turns out my friend hasn't checked his tranny oil in oh...probably a few years. Lol. He always wondered what that filler cap was for, lol. Its a 1972 2 stroke 350 (GT?).

It calls for 20-40 oil. Would Rotella 15-40 work or should I head to a classic Suzuki forum to be sure?

Tell your friend to get the proper factory Suzuki service manual for his bike and perform some maintenance.

That is likely a 380GT, a very nice bike. Are you sure that it is the transmission oil and not the oil injection system? If either are empty, major repairs are likely in order.

No eBay APP ID and/or Cert ID defined in Kunena configurationThis is a start--

If it is the trans oil, Rotella should be ok.

Yes he had better be sure it's getting 2 stroke injection oil.

TexasKZ wrote: That is likely a 380GT, a very nice bike. Are you sure that it is the transmission oil and not the oil injection system? If either are empty, major repairs are likely in order.

Positive. The injection reservoir is above the tranny

Kapahulu wrote: Yes he had better be sure it's getting 2 stroke injection oil.

I don't think putting that in the tranny will be helpful though.

He has the owners manual. It called for 20-40w. I do think its the 380.

He's had and ridden the bike for many years. I've been riding with him for 6 years. I don't know if he just forgot about the tranny or just never knew. I think he never knew. He's a bright guy (a doctor) but not a mechanic, and not young so he may be getting forgetful too.