XJ 650 speed, rpm, gearing general questions.

I finally got my Maxim out for a fairly decent ride yesterday (about an hour in the afternoon). Except for some minor tweaking and tuning, she's running good. I was trying to get a feel for how it pulls throughout the rpm range and see if I can guage my jetting by feel (until I get the tools and time to really synch and colortune the carbs).

Anyway, I have aftermarket gauges (speedo and tach) and I don't think they're right....either one. The tach just seems to not react as quickly as the engine. I bought it on ebay and it was recommended for "most four cylinder metric bikes).

In general it feels to me that the bike rev's out very quickly and tops out early....if it was a chain drive, I'd be re-gearing for sure. It's very quick, but seems to be winding out and not going very fast. I was on the highway and the speedo was reading 75mph but I doubt it's accuracy and it felt like the rpm's were high.

Can someone give me a feel for what speeds are "comfortable" on these bikes (1981 XJ650) AND what tach speeds typically relate to what speeds (ie. my bike reads 4,000 on the tach at 60mph, or something like that)?

In the meantime, my wife is going to follow me in our vehicle and give me some idea about how fast I'm going this weekend.

Thanks!

 

fwiw:

on my xj700, in 5th (final) gear:
4000rpm = 55mph, roughly.

 

With the DOHC sitting right beneath you valuables, it feels like the bike is over-revving a lot, sometimes.

Naturally,, you need to calibrate the Tach to see what the situation is. I'll chime in with my complaint on 5th Gear.

I feel that may 5th Gear is to closely matched to 4th. I'd like it to be an overdrive rather than just another change-up.

I'm forever "Checking" to see if I'm actually in 5th rather than in 4th on the open road. Makes me wish that it was a 6-Speed.

 

Same, always checking to make sure I am in 5th, and the engine sounds like it is revd fairly high all the time to me on my xj650.

 

My 650 Maxim (stock gauges) turns just a hair under 6K at 70 MPH (5th gear). Seems like riding a chainsaw (hearing protection!).

I'll agree with the others. It would be nice if 5 was an overdrive of 30% or so.

Incidentally, 4th gear pretty much correlates with the speedometer (4Krpm = 40MPH, 5500rpm=55MPH).

Electronic tach should be pretty straightforward. I'll place my money it's your speedo that is off.

 

Thanks. BTW, it's a mechanically driben tach...right off the cable out the front of the engine.

 

I cancel my bet then.

 

Rick if you had a 6 speed you would always be looking for 7th gear

 

550' have 6th gear .....and Yes.

 

I agree about 5th Gear. I am constantly hunting for 6th. Especially when you don't shift out of 4th until 9k rpm's. 5th just seems a bit of a climax killer. I think I'm going to grind myself a new 5th gear when I get back from my Europe trip in September. I think the bike would be better on gas and more enjoyable if cruising speeds were achieved at a lower rpm.

I wish I had thought of this before. Maybe I could have got it done for my maxim before I took it to Europe. Would have made the Autobahn more fun.

 

Is this a possibility? Or should i say feasiblity? I'd be interested in buying a replacement 5th gear if it would achieve the overdrive we all seem to want.

 

Well it's a possibility for me since I work at Western Canada's largest custom gear manufacturing shop. To make a new 5th gear you actually have to make the mating gear as well. I wish I had brought my manual in to work so I could work out the math on it. I'm curious if 5th was set up like a normal overdrive gear. Typically your second from highest gear is 1:1 and the top gear is 10% over that.

What I will do is when I get my maxim buttoned up and ready to go I will tear the transmission out of my Seca. I'll bring it in, do a hardness test, and then engineer up a new gear set for 5th. I'm thinking I would go as high as a 20% increase over the current ratio. Unless I find out that 5th is 1:1 in which case I will go 25 - 30%

There's no shortage of horsepower so I don't foresee too many issues. But we'll see. It's kind of an ambitious project.

 

I hope you'll keep us posted in you endeavor to exchange 5th gear for an overdrive.

That's an ambitious project.
I've never heard of it being done.

I know I'll be interested to see how it works out, because I'm alway looking for another gear ratio when cruising down the highway on my Maxim.
The 5th gear presently in the bike just don't cut it for all day riding.

 

I'd be interested in a taller 5th gear as well.

 

If you can get it worked I think you might have everyone choping at the bit to get it. Good luck

 

I just put my case back together but i'd gladly split it again to swap 5th gear. Keep us posted on everything. If you get it right, i'm sure you could make a few extra cents from some of us here.

 

I second that, I would buy one.

 

Me and my visions of grandeur! What have I gotten myself into? lol

On a plus note my pipes just got back from ceramic coating. Satin Black. Very sweet.

 

:lol:
I thought this same thing the other day.
I just ripped through 3 gears, figured I must be flying, looked down 65 mph.
hahahaha.

 

Is it ok to run these bikes all day at 70 mph plus? Mine seems to be at around 6400 RPM at this speed.

 

It OK to run the Bike with the "Tach-in-the-Black" ...
All day and night.
24/7/365

Just stop for gas and check the oil when you do!

 

Could you run a larger diameter wheel, or is that just plain stupid?

 

A larger diameter wheel would give you better highway speeds for sure. Of course you're speedo would be inaccurate.

 

No, your speedo would be fine, as it reads from the front wheel on XJBikes.

Changing rear tire size on a CAR changes the speedo.

And I'll buy an overdrive 5 TH gear from you also.

 

That was a rookie mistake on my part. But in my defence it was Canada Day yesterday and I overindulged.

 

EDIT: Never mind you got it...


But Yes a higher 5Th would be great. I've done it many times here looking for that extra invisble gear. Can nail all the invisble one's before 5th.. just never a 5-1/4 5 - 1/2 5 -3/4 gears =)

 

I'll get on it September the 3rd

 

sept 3rd seems random... unless i missed something.
haha.

 

Read his sig he's going to tour europe.

 

oh yea! i remember that now. haha.

 

The way things are progressing though I may have to change the signature to pushing his XJ650 through Eastern Europe.

 

Oh no, I hope it's not that bad.

 

No. I'm just running out of time. I degreased the engine last night and I'm having a quilting bee with a couple of friends friday night. We'll disassemble the top end of the engine. Take bore measurements and start lapping valves. I'm hoping it will all go smooth. But if I have to bore 1 size over that adds days to my schedule. The rolling frame is practically back together. Just a little cosmetic work, my viper fairing/cowl just arrived so I'll need to get that painted up. New tail light and signals (LED thus new relays). Plus my ammo cases arrived and I need to fab up mounts for them to be used as saddlebags.

Actually when I write it down it doesn't seem too bad. All things being equal and I don't open up a hornets nest when I crack open the engine.

 

Good luck man! post your results.

 

Anyone heard back on this thread?
I'd love a taller 5th, too!

 

Not on this topic but I was glad to see he must've returned "home" safely since he posted here on October 3, 2008 http://www.xjbikes.com/Forums/viewtopic ... tml#110188
Maybe he had too many beer donations on his trip and forgot about this idea. :lol:
I have no clue if I could afford to buy one if he made one but I'd sure like to know what his calculations/possibilities were on the subject.

 

I guess you missed the other Thread ...

"Showing Pictures of My Bike To Europeans!"

Put me down for 5-Bucks on betting he made it.
I hope he did.
I was rooting for him.

 

lets say he could build one for all of us.... would it be as simple as pulling the tranny and swapping the old 5th out for his modded one?

i guess what i am asking is, what all does this entail?

 

Should just be a swap of the 5th gear drive and driven gears. The only thing that would change would be the number of teeth on the two gears.
Every thiing else would stay the same.

I'm going to look at the "other" thread mentiioned above. Hope there is tri story there!

Loren

 

Hound, You had better opt out of the 5th gear overdrive program. 65 mph in 3rd and you were disappointed......... If you had an overdrive gear how would you be able to keep that surplus change in your back pocket??? 8O

Or better yet, overdrive the first four gears and underdrive 5th gear. She'd be a dog off the line and just as you got her up to speed the tach would peg as you shifted to 5th

140 mph is just too fast for school zones!!!

BTW My other ride has an LCD display next to the digital clock that shows what gear you're in. Doesn't say much for Beemer riders does it?

Loren

 

It's the bike, not the rider. If you can't hear or feel the engine, how are you supposed to know what gear you're in?

I've ridden one of those big Beemers before, the complete silent smoothness was spooky.