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Old 12-10-2004, 12:04 PM   #16
creeper
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Quote:
Originally Posted by GT-STMC
I'm one of the "new crop" of 640 owners.
Refering back to this post:
Is there a schedule or process for this here ?
I've searched (but have trouble with the Search engine) and couldn't find one.
The point I was making for Nate's benefit is that with a freshly oiled filter, where one might get a bit heavy handed with the application of oil, or not heavy handed with the removal of the excess... will have a "temporary" rich condition... rich enough to foul plugs. Something to consider when your 640 will only go 85 mph.

Filter servicing is (for most of us) based on our off-road use. There is a mileage based service interval in the owners manual (and a reference to service in dusty conditions as well), but I think everyone ignores it and services/replaces the filter "as needed".
Lots of methods, filters and oil brands in use here... You'd have to poll the population to see what's popular.

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Old 12-10-2004, 01:42 PM   #17
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I think Creeper makes an excellent point and I also agree that Flanny has been a big help to me and others.

When you simultaneously change eight things at once based on some "hot tip" on the internet, you run the real risk of creating some odd interaction of factors that will be difficult to diagnose. Also, any change brings with it the possibilty of error and when you only change one thing, you have a much better handle on where you might have screwed up if something goes wrong. Finally, going slowly and methodically, with frequent tests and checks, allows you to get a handle on what things work and what doesn't. Each bike has its own personality, we ride in different climates, and different riders prioritize things differently - one size doesn't necessarily fit all.

Here is chronicle of my experience: I bought a well-used but basically stock 2000 AdvR a year ago. On tuning, it had a very slightly bigger main jet (145 vs. stock 142.5) but that was about it. It ran Okay, but was pretty snatchy and vibey with a 92 mph top end. I went through the following succession changes:

1. Thorough cleaning, oil change, chain cleaning/lube, and air filter maintenance. Just having a clean, well-oiled chain made a big difference in low-speed running. Top speed when up a couple.

2. Bumped idle from 1400 to 1600 RPM. Smoother idle and better behaviour on decel - before it would snatch below 2K, now it would decel down to idle pretty smoothly.

3. Retorqued motor mounts and adjusted valves. No change I could tell.

4. New plug. Idled better, no other change.

5. Competition (screened) side airbox cover, left snorkel in. Biggest change of any mod I made. Top end increased 5 mph, ran better all around, but did seem lean across the board. Plug checks with throttle chops showed top end leanness.

6 Raised needle one clip. Seemed to run better through mid-range, but not dramatic.

7. New SXC silencer replaced stock SuperTrapp with 12 discs. Surprsingly not much change, probably because ST had so many discs. Less weight and better looks though.

8. 155 main jet. Much smoother top end - now going about 101 indicated. I suspect I can get a little more top end with 160 or so, but plug checks are good, bike runs well, and I'm getting nearly 50 mpg.

9. One more turn on fuel screw. Completely eliminated a bit of popping on decel. Bike now pulls fine from about 2K with light/moderate load, although it still prefers 3K and up.

I may try the drilled slide at some point, experimenting with a single-taper needle vs. the stock double-taper might be fruitful, and I think a 160 or 165 main might give me a little more top end. But overall, I'm very, very happy with the way the bike runs now. If I make any changes, they'll be done slowly and I'll roll back if they don't work.

Or I may just ride the thing. I bought it to ride, not wrench.

- Mark
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Old 12-11-2004, 05:13 PM   #18
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Quote:
Originally Posted by ktmnate
I'm gona finish playing with it on Saturday. I decided to go snow skiing tommorow. I will keep you updated.
Thats funny. I forgot that there was another type of skiing. Winter sucks.

Nate, another basic question that I have been the victim of....

Did you happen to 'bump' the electrode of your spark plug in your tinkering session?

Creeper,
How's the jeep?


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Old 12-11-2004, 07:08 PM   #19
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You guys are right on the money with the whole "experimentation" thang.

I've always said that jetting is a work in progress. As I ride (any bike), I am constantly analysing the jetting as I roll the throttle or just ride at a steady throttle range (especially with the throttle housing marked). Over the years, I've concluded that I am pretty much never happy with jetting. There is always a little "this" on a particularly cold morning, or a little "that" as the air filter get dirtier. I'm constantly making mental notes like this: "hmmm...I'm gonna have to tweek the idle jet this afternoon if it gets much hotter, it's been a while since I cleaned my filter, and the last ride was dusty, so I'll probably wind up a little rich...I'll have to pay attention again this afternoon.."

Jetting on a carburated bike is only perfect the day is is sitting on the dyno. As soon as you leave the shop and the air temp changes, or the filter gest dirty, or as your valves wear, the jetting is wrong.

So, it's much more a question of coming to really know the bike, rather than reading a post on the internet about what the right jetting is.

My guide was more to show people HOW to do the jetting, not what exact jets to use.

I always say it took me a whole season to Jet the BST, and then the fall came, it got colder out, and the jetting went to pot again. Then the next season, I got the TM40 carb, and it took me all season to get that right as well. And again, the fall came, and the cold weather messed things up again. BUT, because I have learned the difference betwen a lean idle circuit and a rich needle, I have always been able to get my bikes close, and to know when the filter needs to be changed, or when the season requires a drop of main jet. That's what's important!
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Old 12-12-2004, 06:58 PM   #20
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Quote:
Originally Posted by creeper
The point I was making for Nate's benefit is that with a freshly oiled filter, where one might get a bit heavy handed with the application of oil, or not heavy handed with the removal of the excess... will have a "temporary" rich condition... rich enough to foul plugs. Something to consider when your 640 will only go 85 mph.

Filter servicing is (for most of us) based on our off-road use. There is a mileage based service interval in the owners manual (and a reference to service in dusty conditions as well), but I think everyone ignores it and services/replaces the filter "as needed".
Lots of methods, filters and oil brands in use here... You'd have to poll the population to see what's popular.

Creep
Sorry it took so long to get back. I was out playing in the snow and then chasing BMW's with the 950. Anyway the bike is running better than ever, it's just the top speed. I have decided to take the "one adjustment at a time" Today it was the air filter wich wasn't very dirty. I did find the air box cover was almost pluged. I cleaned all that out and will test tomorow. I also want to thank Flanny for all the work he did on the 640 and sharing with everyone. I am using his guide as a guide. I was posting to the list hoping that I left something out that someone would refresh my memory.
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Old 12-12-2004, 07:02 PM   #21
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Quote:
Originally Posted by dirtydeeds
Thats funny. I forgot that there was another type of skiing. Winter sucks.

Nate, another basic question that I have been the victim of....

Did you happen to 'bump' the electrode of your spark plug in your tinkering session?

Creeper,
How's the jeep?


Dirty
I love all kinds of skiing (only when I can do it). I don't thin it could have damaged the sparkplug. What I am now doing is one thing at a time. I want to know what it is that is causing this condition. Other than top speed, the 640 runs like a champ! I will keep the list informed.
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Old 12-12-2004, 07:04 PM   #22
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Quote:
Originally Posted by markjenn
What was the top speed before? Most will do around 100 indicated on the IMO, so if this is the case, and it s down to 85 under the same conditions, you're looking at 25%+ drop in power. And engine power in a four-stroke doesn't change drastically with minor adjustments in jetting - if you plot hp vs. a/f ratio, the curve is very flat for anything near the optimal ratio, so you're not going to get a 25% hp decrease with sub-optimal jetting unless the current jetting is WAY off. I don't think the main jet is the culprit.

I suspect something happened in the mods where you're not getting the throttle all the way open or where the slide is getting hung up. Or some other restriction on the intake side - I've seen bikes run terribly where the only problem was over-oiling of the filter or oiling the filter while it was still wet from cleaning. This just doesn't sound like jetting tweaking issue.

FWIIW, I've never "drilled my slide" and have never felt the need to. The bike runs great with tweaks in the main jet (155), raising the needle one clip, and a slight richening of the idle mixture. YMMV.

- Mark
I am almost suspecting the slide. I have had it apart again and inspected. It all looked good but didn't do much for top end. Everything looked like is was sealed correctly. It's gona take me several weeks to sort this one. I am only changing one thing at a time.
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Old 12-13-2004, 06:18 PM   #23
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Ok, I played with the bike and got it up to 102 (On the GPS not IMO). Almost there. I just changed the jet to a 165 just to see what will happen. The problem was the ruber boot wasn't on all the way! It was off on the underside and I couldn't see it. Just another bone-head move! And my wife says I'm dangerous.
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Old 12-13-2004, 06:32 PM   #24
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Quote:
Originally Posted by ktmnate
The problem was the ruber boot wasn't on all the way! It was off on the underside and I couldn't see it. Just another bone-head move! And my wife says I'm dangerous.
I'm not going to say a thing... glad you found your problem.
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Old 12-13-2004, 06:34 PM   #25
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Oh, that was only part of the problem. I put new grips on and man does that help. I swear the new grips gave it an extra 5 hp.
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Old 12-13-2004, 07:18 PM   #26
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Quote:
Originally Posted by ktmnate
Oh, that was only part of the problem. I put new grips on and man does that help. I swear the new grips gave it an extra 5 hp.

Awesome! So she was really lean! Good on 'ya for finding the problem.

Pump up your tires to 40PSI, and you'll pick up another couple of mph. Also, don't forget to shave before you go out for your test run..(every ounce count 'ya know)
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Old 12-13-2004, 09:36 PM   #27
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Quote:
Originally Posted by ktmnate
Oh, that was only part of the problem. I put new grips on and man does that help. I swear the new grips gave it an extra 5 hp.
Did I mention I wasn't going to say a thing?...
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Old 12-30-2004, 06:16 PM   #28
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Quote:
Originally Posted by Flanny
You should experiment with the main jet. For top speed and WFO, that is the circuit in question. By definition, the right main jet is the one that gets you the best speed for a given section of road....

You are probably too rich on the main jet. I think with my stock exhaust, I never needed more than 157.5 at sea level on the BST40. So, go back and re-try the 157.5 as a starting point, and then try each interval of 2.5 until you get to 165. (my guess is that a 160 is probably the one you need for best top speed).

Another approach would be to put 3 disks back in to your exhaust to lean out your mixture, essentially "simulating" a move toward a 160 MJ...that will give you an idea of which way your jetting needs to go. If adding three disks back in to your exhaust improves top speed, then you were too rich...

Good luck...remember jetting is pretty much always a work in progress....and you just have to keep trying different jects until you get it right.
Hi there Flanny'
I had my bike rejetted with exact spects you send it to me while ago. Results was great however I .sold the bike to "Boulder Boy" from Boulder and he wonders what do you suggest for 5500 feet high altitude?
Thanks in advance
Moto
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Old 12-30-2004, 09:05 PM   #29
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Quote:
Originally Posted by ktmnate
Oh, that was only part of the problem. I put new grips on and man does that help. I swear the new grips gave it an extra 5 hp.
Yours is an '02 right? What kind of grips did you use? I have an '03, so what's the conversion, colour change etc...? Maybe creeper can chime in with some help...

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Old 12-30-2004, 09:18 PM   #30
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Quote:
Originally Posted by Maxmoto
Hi there Flanny'
I had my bike rejetted with exact spects you send it to me while ago. Results was great however I .sold the bike to "Boulder Boy" from Boulder and he wonders what do you suggest for 5500 feet high altitude?
Thanks in advance
Moto
Well...It's a whole new ball game. I've never jetted for that kind of altitude, but I would suggest that stock air pilot (1.2) and jetting back down to 152 or 155 MJ would be more in the range.

He'd have to experiment on the main jet in particular and get back to us with the result...I've heard rules of thumb like one MJ size down for every 2000ft of altiture, but I've never tried them in practice.

Any other people that are high can chime in anytime (litterally or figuratively).
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