Triumph Rat Motorcycle Forums banner

1 - 2 of 2 Posts

·
Registered
Joined
·
85 Posts
Discussion Starter #1
Hi guys,

My 72 Trophy 650 TR6C doesn't have a tach and I'm wondering about general engine revs at certain speeds. It's a 4 speed but since it's a C model the gearing is a little lower than a regular 4 speed. Doesn't seem like it would make a huge difference, I probably just have to shift sooner than most other Triumphs. And naturally I won't have quite the same top end. Not worried about top end though. Rode a friends honda hurricane to ~120 mph on a kansas highway so been there, done that. Ultimate top speed is not the reason I got this Triumph.

my bike:

1st: 12.73
2nd: 8.83
3rd: 6.48
4th: 5.22

Regular:

1st: 12.08
2nd: 8.36
3rd: 6.14
4th: 4.95

So far I've only gotten the bike up to around 55mph and it seemed to like it. Haven't taken it on a road with a higher speed limit yet. First Triumph, first bike I've personally owned. Sounds good, seems like it would go faster. I'd like to blame not 'getting out on the highway and just going for it' on the fact that my tires look kinda old and have a few cracks in the sides, but in reality I think I'm just kinda scared for some reason. :) Finally got a proper helmet this week though and I cruised the bike up a nice windy mountain road and back down again with no issues (other than some backfiring when engine braking). So I'm getting there. :)

Nonetheless, when it gets up to 55mph, the engine starts singing and smoothes out really nicely. I'm just wondering about how high you think the RPMs are in 4th gear at 55mph so I can get an audible idea of how fast my engine is turning over when in lower gears. Don't mind shifting by the 'feel of things' I just don't really have a baseline, let alone a redline.

What speeds do you generally shift at? What is 'redline' on these bikes anyhow? NO, I don't plan on redlining it - that's kinda the whole reason I'm curious. I want to keep it safe. Fun and exhilarating, but safe (for myself and the engine)

If any math whizzes care to speak up on just how much of a difference the slightly lower gearing makes, I'm all ears. That stuff makes my head hurt (especially when figuring out all the weird gearing stuff on my jeep, but that's another forum).

Thanks so much for any input!

sb
 

·
Registered
Joined
·
85 Posts
Discussion Starter #2
she goes fast

And here I thought getting one of you guys with the bonnies to take a peek at your tachs while going 55mph in 4th would be tossing ya a softball question. Or at least an excuse to take the bike out on the highway (gotta take the bike out for a ride to help a stranger, dear) :) Don't hold out now. I know you've got tachs. I've seen em, so fess up what's your engine RPM when going 55? :p

I read a magazine article recently that stated Ed Turner had a dictum that a 650 engine should never go over 6500 RPM, yet I found some literature that states my bike gets max HP at 7000 RPM and max torque at 6250 RPM. Not even looking to max it out, just curious.

Meanwhile, I decided to just say 'screw it' and have been taking the bike on the highway to work everyday this week and it runs pretty good. Well, up until it hit 70MPH the first day. Then it started missing. The last time it missed like this I didn't have the two carb/intake bolts on tight enough and it would miss when under load around 40-45 MPH.

Once I had the missing issue on the first day I decided to keep it at lower speeds the rest of the week - around 55 MPH - it doesn't miss unless I decide to pass someone, go up a hill hard etc. So based on past experience I'm thinking it's probably a leak between the carb/spacer/intake somewhere. If I tighten those two bolts down anymore the throttle sticks like crazy though! Gonna head over to isles motorcycles in a bit to get some gaskets and spend a couple hours taking that approach until I send in the carb for slider plating this winter.

It was kind of a fright when I looked at the engine after arriving at work the first day. There was a nice stain of oil going down the front of the crankcase and some oil on the bottom half of the front pushrod. No oil dripped all day long though so I think it was just some oil that got hot and while vibrating at 65-70 mph it just spread out. Wiped it off and it hasn't come back. Keeping my eye on it though.

Still have to figure out why it's backfiring when engine braking. Valves seem good. Gonna go ahead and try loosening em up a small bit if I can get a wrench on the locknut. Might check timing. But I'd think I'd have more consistent issues if it was a timing problem.

Gonna bounce all this off Greg Isles... he's a good bloke and generally steers me in the right direction if I'm spending money and asking easy questions nicely. :) He's been honest and has actually told me not to spend money on a few parts as they wouldn't do me any good - so for those in denver or the rocky mountain region I'll vouch for this guy (not to mention he has at least 15 brit bikes in the shop).

Well, that's my digital diary entry for the week. Thanks for reading. (and if anyone would care to post their engine RPMs in 4th at 55MPH I'd be most grateful). :D

Put a couple nice pics from a cruise up lookout mountain down below. Feel free to take a gander.

shawn
 

Attachments

1 - 2 of 2 Posts
Top