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Discussion Starter · #1 ·
Hello all- just a general inquiry: what are safe highway RPMS and Speeds? I find I’m doing around 4K RPMs at 70ish MPH. Is this ok for the engine? What’s the cruising range in 5th gear? It’s a 2004 Bonneville t100 for reference. Thanks
 

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If your bike is a 790 I suspect the front sprocket has been changed from 17 tooth to 19 tooth or a taller rear tire installed. In the long run it probably doesn't make much difference as to how long the engine will last. At the speed and RPM's you'r talking about I can't see that engine lasting much more than 150,000 to 180,000 miles.:unsure:

Happy motoring, R.
 

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4000rpm is little high. its 110km legal speed here in aus on the freeways, and mine sits around 3300rpm that's about 68mph my bike is 2009 efi
 

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I have a 2006 T100 and I spin 3K at 50mph in 5th. Seems high to me but I don't have another point of reference to say if it's normal or not.
 

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2004 Daytona 955i, 2018 Indian Roadmaster, 2014 Triumph Scrambler, 1980 CB650C in resto
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A modern engine (post 1990-2000ish) on any motorcycle should be able to do 4000 rpm pretty much endlessly.
 

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My 05 T100 ran all day at 3500rpm and returned 65mph. It was a 865 motor with 18t front sprocket and 43 t rear sprocket. BTW that's the same rpm's and speed my 08 T100 runs at.
You worry to much, just ride and enjoy the bike.
 

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Discussion Starter · #7 ·
My 05 T100 ran all day at 3500rpm and returned 65mph. It was a 865 motor with 18t front sprocket and 43 t rear sprocket. BTW that's the same rpm's and speed my 08 T100 runs at.
You worry to much, just ride and enjoy the bike.
I worry way too much. Been a habit I haven’t broken since I was a wee boy.
Im a glutton for punishment tho- on top of these motorcycles I have an old quirky car too. My friends all insist that I just hate myself haha
 

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Here are my notes on my 790 engine 2002 that I have added a 19T front sprocket. I like the lower RPMs at speed. It looks to me that someone added 19T to your bike also.

Stock Gearing : 17/43 chain is 525. Optional : Front sprocket 19T British Customs (Part: BC704-001-19) 19T = 3000k at 55mph / 3250k at 60mph / 4200k at 75mph.
 

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2012 T100 efi with standard sprockets for that year...70mph is 4k rpm, so I'm adding a 19 tooth front to reduce 70mph to approximately 3,750 rpm. These engines are solid and as long as you don't phuk up your impending oil change:rolleyes::D you should be fine for many years/miles/kiloflogs/parsecs etc
 

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I run 17/43 gearing on my 2010 T100, and at least half of the miles on my bike are 80mph/5000 rpm commuting on the interstate to work. Maybe the first motor would have lasted more than 160k miles if I didn't run it as hard?

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Stresses on engine components are generally linked to the square of the rotation speed. So keeping the math easy, look at the ratios...
Square of 4 (4000 rpm - drop the zero's) =16
Square of 6 = 36
Square of 8 = 64
That should give you some idea of the stress the engine is under at 4, 6 & 8K rpm (if it will go that high)

For best fuel mileage, you need to run the engine at peak BMEP. It's what the car companies do and they play with things to drop BMEP to low rpms and then try to keep the engine spinning at that rpm with CVT's or 8 speed transmissions. Low rpm does not necessary mean better fuel burn and cylinder pressures go up.
 

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I worry way too much. Been a habit I haven’t broken since I was a wee boy.
Im a glutton for punishment tho- on top of these motorcycles I have an old quirky car too. My friends all insist that I just hate myself haha
Pics and make of the old quirky car?
 

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What is the red line of the bike because theoretically you can maintain 75% of redline without incurring any extra wear and tear. For example, I have a 2016 Thunderbird LT which red lines at 6500. So theoretically, I can maintain 4875 rpms without a lot of concern. I don't do that for extended periods though, even though my friend who is an ace mechanic laughs at me.
 

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I’ve literally beat the hell out of a 2004 Speedmaster 790 and she’s still hanging in there at 115K miles, really needing a new timing chain, crank, and maybe even a lower case depending on what the big end bearings would look like. But I still ride her.

I’m thinking more like 80% of the miles have been easily above 4000 rpm - most over 5000. I was blessed early on with the kind tip to generally upshift at about 5000 rpm on that engine. It totally changed the way I rode the bike and helped me grow a great deal into the spirit of the sport, as this is the first motorbike I have ever ridden or owned.

It came with a 16t front sprocket and I tried 17’s and 18’s for a set of tires and chains or two then put the old 16t sprocket back on. I knew immediately I would never go bigger again.

I’ve sampled every oil change on it, very 4K miles as my book said, but using the incorrect viscosity of motor oil (Blue jug Rotella), and the reports always told the tale. She was healthy. Right down to when the timing chain started began consuming the chain blades. Blades have been replaced now but she’s not healthy or fit for anything more than neighborhood boulevards. I lack knowledge of a reliable shop to trust the engine with, and struggle with whether I would want to do that to anybody. I’m in the Classic British car repair business and motor overhauls are endless projects that can really bog a shop down. I’d love to do it myself don’t don’t want to commit the time. (I’d rather be riding.)

Always garage kept, she still looks all bright and shiny. In BLACK. The FASTEST color.

I wouldn’t change a thing if I had to go back and do it again. The awe, the smiles, and the utter contentment she’s blessed me with over the last 17 years are priceless. She did not change my life as much as she gave my life a direction. A direction to GO MY OWN WAY.

If you want to wear one of these motors out, you’d better pack your lunch.
 

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Discussion Starter · #19 ·
I’ve literally beat the hell out of a 2004 Speedmaster 790 and she’s still hanging in there at 115K miles, really needing a new timing chain, crank, and maybe even a lower case depending on what the big end bearings would look like. But I still ride her.

I’m thinking more like 80% of the miles have been easily above 4000 rpm - most over 5000. I was blessed early on with the kind tip to generally upshift at about 5000 rpm on that engine. It totally changed the way I rode the bike and helped me grow a great deal into the spirit of the sport, as this is the first motorbike I have ever ridden or owned.

It came with a 16t front sprocket and I tried 17’s and 18’s for a set of tires and chains or two then put the old 16t sprocket back on. I knew immediately I would never go bigger again.

I’ve sampled every oil change on it, very 4K miles as my book said, but using the incorrect viscosity of motor oil (Blue jug Rotella), and the reports always told the tale. She was healthy. Right down to when the timing chain started began consuming the chain blades. Blades have been replaced now but she’s not healthy or fit for anything more than neighborhood boulevards. I lack knowledge of a reliable shop to trust the engine with, and struggle with whether I would want to do that to anybody. I’m in the Classic British car repair business and motor overhauls are endless projects that can really bog a shop down. I’d love to do it myself don’t don’t want to commit the time. (I’d rather be riding.)

Always garage kept, she still looks all bright and shiny. In BLACK. The FASTEST color.

I wouldn’t change a thing if I had to go back and do it again. The awe, the smiles, and the utter contentment she’s blessed me with over the last 17 years are priceless. She did not change my life as much as she gave my life a direction. A direction to GO MY OWN WAY.

If you want to wear one of these motors out, you’d better pack your lunch.
Oh man what a great deal of advice all rolled up into a nice little read. Thanks for the reply!
Only thing is, no blue bottle rotella? I’m using it, 5w40, in synthetic. Should I change?
 
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