DR650 790 Big Bore Installation and Review

[doug s.]

Originally Posted by doug s.

nice! congrats!

but, i don't understand why the rpms would not be exactly the same if you didn't change gearing. if you were at 4700rpms at 74mph before, changing the engine displacement alone shouldn't affect that... you should still be at 4700rpms at 74mph...

doug s.

Originally Posted by planemanx15

Even though the gearing is the same, the bigger engine works less to obtain that speed. At least that's my theory

regardless of how much the engine is working, (i suspect it is actually working more - making more hp at any given engine speed), it's still turning the same rpm's to get the wheels turning their rpm's... math is math...

now, because the engine is making more power at any given rpm, you could put a 41t sprocket on the rear (or a larger diameter tire) and lower your engine rpm's at any given mph, and the bike will still pull hard... you are already running 17-42; did i read that correctly?

doug s.

[planemanx15]

Originally Posted by doug s.

regardless of how much the engine is working, (i suspect it is actually working more - making more hp at any given engine speed), it's still turning the same rpm's to get the wheels turning their rpm's... math is math...

now, because the engine is making more power at any given rpm, you could put a 41t sprocket on the rear (or a larger diameter tire) and lower your engine rpm's at any given mph, and the bike will still pull hard... you are already running 17-42; did i read that correctly?

doug s.

Yes I have a 17-42 set up. I went to that because when I went to a lower profile tire, my rpms jumped up.

[planemanx15]

Originally Posted by vicster

Did you notice any increase in engine vibration with the 790 kit installed?

No increase noted at all..yet. it's only got 10 miles on it. Hopefully this week ill be able to ride more. I did notice it was quieter, but than I realized my skid plate is off. I never realized how much noise that reflects. Ill be doing some sort of sound damping next.

[barko1]

I would guess that stock header pipe is really choking thing up with the bigger displacement. It seems small for the 650 so it must be quite restrictive on the big bore. Thanks for the write up

[VooDooDaddy]

Mr. Planemanx,

Did you happen to measure the piston ring end gap before doing the final install? If so, was is spot on or did you have to open it up a little?

Thanks,

Trent

[planemanx15]

Originally Posted by VooDooDaddy

Mr. Planemanx,

Did you happen to measure the piston ring end gap before doing the final install? If so, was is spot on or did you have to open it up a little?

Thanks,

Trent

Trent, Mr. Planemanx is my father, you can call me Joe. lol.

I did not measure the piston ring end gap. Procycle does supply the measurements with the kit.

[VooDooDaddy]

Originally Posted by planemanx15

...call me Joe. lol.

I did not measure the piston ring end gap. Procycle does supply the measurements with the kit.

Joe it is....

Thanks

[Jimmy the Heater]

Had no idea that this kit even existed. Watching with interest

[planemanx15]

Ran the bike for another 30 minutes today, got the oil hot, various RPM's. Its all good! Looks like its going to be above freezing and dry at the end of the week, so expect a report very soon.

[neo1piv014]

Originally Posted by planemanx15

Ran the bike for another 30 minutes today, got the oil hot, various RPM's. Its all good! Looks like its going to be above freezing and dry at the end of the week, so expect a report very soon.

Can't wait to see how she runs. Seeing the whole process from step 1 like this actually makes everything look fairly accessible. When you talk about doing it all in one solid day's work, that's something that a lot of us could see ourselves doing.

[planemanx15]

Got to go out today. Did about 60 miles and it felt great. Engine pulls from way down low, it has loads of power, and maybe a slight increase in vibrations.

Then came a problem....

On the highway coming back home, i was holding a steady 80 mph for about a minute. Just then, I heard a loud metal sound coming from below me, and the engine felt like it lost a bunch of power. I pulled over and it died. Before getting off the bike, I tried to restart it, and it started, but wouldn't idle. I got off the bike, and listened. It sounds like its coming from the right side, maybe the valves. Since the bike was running, i decided to just go home. It was about 15 miles at 45-60 mph. The metal noise continued to chime but much lower. If I revved the engine, it got louder. I got home and the bike was able to idle. The noise was still there.


I hope that its just a valve came loose and the nut is siting on top of the engine. I haven't opened it, as its way too hot to get in there. Any suggestions if its not the valve? It could be anything, I think the noise is on the right side, but it might not be. Also the engine oil temps during the whole ride ranged from 150*-190*F. I have a plate over my oil cooler, since its in the 30's today. The temps did not increase after this incident.

[VooDooDaddy]

To help pin-point the exact location of this "sound", get a long-handled screwdriver, place the handle against your ear hole and the business end resting firmly on several different places on the engine while its running.

This may help you pin-point the location of the sound. The vibrations/noise will travel through the screwdriver directly into your ear, thus mechanically amplifying the sound through the screwdriver.

Based on your descriptions, it 'sounds' like its either coming from the cylinder head or the clutch area?

[Rob.G]

I'd also consider calling ProCycle and talk to Jeff about it... see what he thinks. He may have encountered this problem before.

Edit: I wonder if it's related to the cam chain tensioner? They sell a manual one that may work better than the stock automatic tensioner.

Rob

[planemanx15]

Adjusting valves did not work, here is a video of the sound::

[planemanx15]

Originally Posted by Rob.G

I'd also consider calling ProCycle and talk to Jeff about it... see what he thinks. He may have encountered this problem before.

Edit: I wonder if it's related to the cam chain tensioner? They sell a manual one that may work better than the stock automatic tensioner.

Rob

Thanks for the suggestion, Maybe the cam chain skipped a tooth? would the bike still run?