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Old 06-23-2012, 07:44 AM   #66271
sandwash
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Stock vs Pumper carb= apples and oranges
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Old 06-23-2012, 07:46 AM   #66272
Albie
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Originally Posted by Snowy View Post
After my "highly controversial" carb mods to the standard carb, I have ridden TM40 equipped DRs and been unimpressed. Yes they went a little harder, not much, but by God they drank a lot more fuel.
I've found it depends on how you ride the bike. My buddy has a stock carbed bike with stock exhaust and only the snorkel pulled. He gets 46 MPG when we ride real easy. I get 40 with my TM 40. When we ride hard, his mileage drops down to 38, mine stays at 40.
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Old 06-23-2012, 08:49 AM   #66273
maynard911
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Originally Posted by eakins View Post
been REAL happy with NGK iridium plugs over the copper version.
bike runs better & starts easier.
http://www.procycle.us/bikepages/dr650.html#engine
Could someone explain to me the 'why' of this. It's not that I disbelieve the statement, I just don't understand why it is true.
It seems to me that the purpose of a spark plug is to provide an air gap for the spark to jump across. I can see where making the electrodes out of unobtanium type metals would make them more durable but why would the engine run better than with a standard plug in good condition?
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Old 06-23-2012, 08:53 AM   #66274
Olas
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Originally Posted by sandwash View Post
Stock vs Pumper carb= apples and oranges
+1

You can try and make the CV carb work like a pumper, but it will never be a pumper. Im glad I ditched mine before I dumped too much time into trying to make it something that it is not.

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Old 06-23-2012, 09:38 AM   #66275
doug s.
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Originally Posted by Snowy View Post
For the steeper shale and rocky trails the modified carb is fine. Any more go and it just wheelspins....

...You need the torque of the engine, and not the power down low with a trail bike. Tractability in the lower rev range, and just off idle. In the videos I shoot where I'm climbing I'm really being careful with throttle control most of the the time to control wheelspin. If it spins on these climbs you lose momentum so fast that literally the rear end will step out, you have to get off the throttle, and forward progress stops and the inevitable crash starts. It may take a few metres and 20 secs to play out, but it marks the beginning of the end on a steep shale climb.

I have the standard carb working so close to a pumper and working so well at low revs and right off idle for the setup on this particular DR that there would simply be no significant gain. I have never had it at wide open throttle on a climb any where ever. I have never needed more acceleration than the standard carb would deliver. I'm riding at the limit of my suspension, my tyres and most importantly my ability when I'm in more technical terrain. The engine doesn't come into it really.

For my other DR that has a DR rear end and Racetech shock internals etc, yes, I would bother. Different geometry, different use, different set up, different result in the dirt and on tar.

My set up on my trail DR is for trail riding. It works best at low throttle, short shifting, using the engines torque. I did a lot of reading and measuring and comparisons between different set ups and their design characteristics before choosing it. All around for what I do I think it's the best set up. Like all things, there's a level of compromise.

It depends on exactly what sort of riding you do, what the setup is on your bike, and where you ride as to the perceived benefits of a pumper carb.

I think guys that fit pumpers and are really excited about it spend more time on tar than I do, and there they have a tangible result.
while i am a tar rider, not a dirt rider, i find your comments interesting, because most of the comments i read from other riders indicate that the pumper offers far better dirt performance, because of everything you mention that is important to you: working best at low throttle, low revs and right off idle; short shifting, using engine torque, etc... i'm happy for you that you have your stock carb dialed in w/your magic touch that makes it so good that, in your words, it's almost as good as a pumper.

most folks don't get their stock carbs almost as good as a pumper, and for those who do, well, as you say, it still isn't quite as good as a pumper. considering that shopping used and re-selling your stock carb will result in a net cost not much more than fiddling w/the stock carb, i still think ditching the stock carb is the best action for most folks. and, for those less inclined to futz, yust buy a new carb already set-up, and plug-n-play. if you can't futz, you will likely also be frustrated trying to properly set up your stock carb. and, based on the overwhelming reaction of those who have gone to pumper carb set-ups, they also think ditching the stock carb was the best solution.

snowy, i can't help but conclude you simply have some emotional attachment to your stock carb; perhaps cuz you are happy you were able to get its performance so close to a pumper. i can understand this. audio is also one of my passions (fortunately my hearing is still in good shape); i have a +10 year old $150 dac that i have tweaked and it acquits itself well when compared to modern dacs in the $8k range... i am not sure it's worth spending that much more to get negligible (if any) improvements...

doug s.
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Old 06-23-2012, 11:10 AM   #66276
Mongle
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Quote:
Originally Posted by maynard911 View Post
Could someone explain to me the 'why' of this. It's not that I disbelieve the statement, I just don't understand why it is true.
It seems to me that the purpose of a spark plug is to provide an air gap for the spark to jump across. I can see where making the electrodes out of unobtanium type metals would make them more durable but why would the engine run better than with a standard plug in good condition?

Going out on a limb here-

Theory #1:The only thing I could think of is the unobtanium plugs produce a Hotter spark (not to be confused with heat range- see below) or a larger spark. It is all about getting a complete fuel burn by the time the piston reaches TDC. Lets call these plugs more efficient at making a charge of fuel burn which would make the engine more efficient.

Theory #2: a lean fuel mixture is harder to ignite then a rich mixture. Maybe the people that feel the diffrence in the plugs have a leaner mixture then those who don't feel the diffrence. The plug is better able to ignite the leaner mixture makeing the bike "feel better". This is why you see cars with individual coil packs now. They need the extra energy because they are trying to get more performance (HP) out of less fuel (milage).


Little info: people have talked a little about heat range but I'm not sure they understand it's intended function. I will try to explain it best I can: The heat range of a plug is how much heat the plug can dissapate before burning up the electrode. The idea behind the heat ranges is to keep the plug clean and from burning up. If you look down in a plug with a light you will see that a "hotter" plug has more porcelain protuding then a "colder" plug. This is to keep the porcelain hot to burn contaminants off of it. The shorter porcelain of the colder plug allows heat to be transfered quicker to the metal body. The trick is to find the proper plug. The most basic way to check you heat range is to look at the threads. You are usually looking for 3-4 threads that show signs of heat. The porcelain should not have any buildup on it either. If you see that there are 7-8 threads showing heat and the porcelain is white from heat (or the electrode is torched off ) you need to go with a colder plug. If you only have 1-2 threads showing heat and the porcelain has contaminants/black you need to go hotter. DO NOT confuse a dark plug with needing a hotter plug. Too many people see a black plug and immediately put a hotter one it. If you have any type of oil burning issue or a rich fuel mixture these things need to be fixed BEFORE determining heat range. Going hotter on a plug does not fix a rich mixture or oil burn issue.

On my DR I saw that the plugs showed 4-5 threads of heat on the stock plugs. I didn't go colder because the electrode looked good and the plug was clean. For my normal riding I felt the standard plug was fine. I also would expect to see more heat on an air cooled engine. If I was going to do track days, lots of sand riding, or anything where the engine would be working hard for long periods I would probably go to the next colder plug.

Hope this helps someone.
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Old 06-23-2012, 11:38 AM   #66277
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Originally Posted by doug s. View Post
feelers, yust fyi, according to jeff at procycle, the 725 and the 780 dyno charts both include upgraded cams and big walve heads. it seems the torque, not the hp is where the 790 really excels over the 725.

in any ewent, my bike, w/stock motor, fcr39 carb, k&n cone filter, hi flow midpipe w/fmf powerbomb header and tsukigi gsxr1000 can and stock gearing, will run all day at 80-85, and pull strongly to at least 100. (according to the vapor trailtech, not the stock speedo). as i don't run dirt w/my bike, i am considering dropping a tooth in the rear sprocket (or changing rear tire to 150/70/17 from 150/60/17) yust to lower the rpms; i am sure the bike will still run 80-85 yust fine...

doug s.

The charts for the Big Bore Kit do include the upgraded cams and says so in the Q&A. The Big Bore Kit charts do not include the Big Valve Head.
In the Big Valve Head Charts, the base 725cc line matches the Big Bore 725cc line in the Big Bore chart. The 725cc w/Big Valve Head output is higher. This supports my assertion that the big valve head is not included in the Big Bore charts.

Also, Hp = (Tq x RPM) / 5252. The horsepower increase is exactly proportional to the Horsepower increase.
Yes, the torque is the DR's strong suit since it can't run high rpms due to heat, but Torque isn't used in those theoretical calculations for top speed - Horsepower is. And, 54 Hp plus another 10% for a big valve head would let the DR beat a 690 - in a drag race....

Yes, my bike will run 80 - 85mph just fine also, but I wouldn't be too keen running it at those speeds for too long. Above 75, and my temperature starts increasing quickly. And boosting the front sprocket to a 16 tooth only drops 85mph rpms by 300 rpm to 5200 rpm.
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Old 06-23-2012, 11:55 AM   #66278
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Originally Posted by Feelers View Post
Yes, my bike will run 80 - 85mph just fine also, but I wouldn't be too keen running it at those speeds for too long. Above 75, and my temperature starts increasing quickly. And boosting the front sprocket to a 16 tooth only drops 85mph rpms by 300 rpm to 5200 rpm.

My engine temps seem to hold out ok with top rpms. my 14t front sprocket has taken me to 95mph but without a fairing or screen, the wind just beats the piss out of you. 70-75mph is my sweet spot. I am going to pick up a 16t c/s but im surprised it would only drop rpm's by 300. i'd have thought much more.
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Old 06-23-2012, 12:05 PM   #66279
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Originally Posted by N.dica View Post
My engine temps seem to hold out ok with top rpms. my 14t front sprocket has taken me to 95mph but without a fairing or screen, the wind just beats the piss out of you. 70-75mph is my sweet spot. I am going to pick up a 16t c/s but im surprised it would only drop rpm's by 300. i'd have thought much more.
I think it drops it 300 if you are using the stock 15T sprocket. Would be more so for you as you are using the 14T. I'm sure someone else will chime in.
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Old 06-23-2012, 12:14 PM   #66280
Feelers
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Originally Posted by gjcarving View Post
I think it drops it 300 if you are using the stock 15T sprocket. Would be more so for you as you are using the 14T. I'm sure someone else will chime in.
Yes, the 300 rpm drop is going from a 15T to a 16T sprocket.
At 75mph, RPMs will drop by 600-700rpm going from a 14 tooth to a 16 tooth front sprocket.
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Old 06-23-2012, 03:32 PM   #66281
ADV8
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Originally Posted by Feelers View Post
This supports my assertion that the big valve head is not included in the Big Bore charts.
I would think so simply because that would be dishonest. (780 and 790 which has no chart?)
I very much doubt Procycle would do that.
The only chart for the big bore and bigger valves is the 725.
It is suggesting that configuration makes similar HP to the bigger engines with stock valves.


http://www.procycle.us/images/dyno/d...725-780-hp.jpg

http://www.procycle.us/images/dyno/d...725-780-tq.jpg

Verses.

http://www.procycle.us/images/bikepa...50/bvhdyno.jpg

http://www.procycle.us/images/bikepa...bvhdyno-tq.jpg

I would think seat of the pants is what it is all about and real world riding.
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Old 06-23-2012, 03:35 PM   #66282
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Originally Posted by Feelers View Post
Yes, the 300 rpm drop is going from a 15T to a 16T sprocket.
At 75mph, RPMs will drop by 600-700rpm going from a 14 tooth to a 16 tooth front sprocket.

What's the difference between a 15 and a 14??

About the same I assume, 300 rpm's?
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Old 06-23-2012, 04:10 PM   #66283
Feelers
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Originally Posted by ADV8 View Post
I would think so simply because that would be dishonest. (780 and 790 which has no chart?)
I very much doubt Procycle would do that.
The only chart for the big bore and bigger valves is the 725.
It is suggesting that configuration makes similar HP to the bigger engines with stock valves.
I wasn't implying dishonesty from Procycle. All I've heard about them is positive.
I was just combating Doug S's assertion that, "according to jeff at procycle, the 725 and the 780 dyno charts both include upgraded cams and big walve heads."
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Old 06-23-2012, 04:13 PM   #66284
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Originally Posted by greener556 View Post
What's the difference between a 15 and a 14??

About the same I assume, 300 rpm's?
Yep!

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Old 06-23-2012, 04:28 PM   #66285
doug s.
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Originally Posted by Feelers View Post
The charts for the Big Bore Kit do include the upgraded cams and says so in the Q&A. The Big Bore Kit charts do not include the Big Valve Head.
In the Big Valve Head Charts, the base 725cc line matches the Big Bore 725cc line in the Big Bore chart. The 725cc w/Big Valve Head output is higher. This supports my assertion that the big valve head is not included in the Big Bore charts.

Also, Hp = (Tq x RPM) / 5252. The horsepower increase is exactly proportional to the Horsepower increase.
Yes, the torque is the DR's strong suit since it can't run high rpms due to heat, but Torque isn't used in those theoretical calculations for top speed - Horsepower is. And, 54 Hp plus another 10% for a big valve head would let the DR beat a 690 - in a drag race....
the fact that jeff at procycle specifically told me that the dyno chart of the 780 motor does include the big walve head as well as the upgrade cam, supports my assertion that the 780 dyno chart includes the big walve head.

i queried procycle directly, because the info on the procycle site is a little ambiguous, imo...

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