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Old 12-16-2012, 03:04 AM   #71866
LexTalionis
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Quote:
Originally Posted by blackcap View Post
for those using the TM40 pumper carb: whats the reliability of this thing like? seems i keep tearing through slides, slide guides and emulsion tubes on the BST. starting to feel like this set is done after only about 10 000km and the set before that was only about 20 000km. i replace them another 2 times and ill have enough money to go for the TM40. so how many kms do people have on theirs and what problems have you had?
Have over 18k miles (you can do the conversion math to kilometers) on my OEM carb, haven't opened it up since I adjusted the fueling at around 500 miles by installing a washer and backing out the A/F screw. No problems with my carb. I do run Techron or that other similar fuel additive whose name escapes me at the moment through it every half year or so. And my carb slide gets lots of action, relatively little constant throttle usage.

Lex
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Old 12-16-2012, 03:09 AM   #71867
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Quote:
Originally Posted by LexTalionis View Post
Have over 18k miles (you can do the conversion math to kilometers) on my OEM carb, haven't opened it up since I adjusted the fueling at around 500 miles by installing a washer and backing out the A/F screw. No problems with my carb. I do run Techron or that other similar fuel additive whose name escapes me at the moment through it every half year or so. And my carb slide gets lots of action, relatively little constant throttle usage.

Lex
yeah i had no problems like this when i was in aus, but ive been in SE Asia for the past 12 months or so now and thats where ive been wearing through the parts so quickly. i was thinking it might be something to do with fuel here, who knows what they put in it (some people still put mercury in the cosmetics). im going to be in this part of the world and central asia/ the middle east for probably the next 18 months so wondering if the TM40 has the same wear issues or i can alleviate some of my headaches by forking out for the new carb. i dont know anything about the TM40 or how it operates.
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Old 12-16-2012, 04:30 AM   #71868
TJWally
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Question 2012 DR650 Suspension

Hi just about to get a new DR650 again and I am going to be upgrading the suspension on this one as the dive under breaking with gear was far too much.

I weigh about 190-195lbs (88kgs) without gear. And I am looking at getting a 7.5kg/mm rear eibach spring and a .60kg/mm front springs with gold valves front and rear. I am sure this question has been asked many times but if you have any idea of whether that would be about the right weight springs or not I would appreciate it.

I will be setting the bike up for ADV riding and commuting - but happy to set it up more suited to dirt than blacktop.

And does anyone know what it would cost to get this done at HOEY racing (Australia)

Cheers,
TJ
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Old 12-16-2012, 08:36 AM   #71869
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Speaking of suspension, I'd like to hear from those who have cut their fork springs to gain some stiffness.

I've got to imagine that since the extra range of the springs is being substituted for firmness, that it becomes a tiny bit harsher for a given outcome than would buying new springs that are just as long as the stock ones, but made thicker.

Anyway, I can't quite see how cutting my springs to save money would be such a bad idea since I'm not creating a Baha racing machine here. The last bike I bought springs for showed me that aftermarket springs were often shorter, anyway, than the originals.

Mambo Dave screwed with this post 12-16-2012 at 08:50 AM
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Old 12-16-2012, 09:37 AM   #71870
acesandeights
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Quote:
Originally Posted by TJWally View Post
Hi just about to get a new DR650 again and I am going to be upgrading the suspension on this one as the dive under breaking with gear was far too much.

I weigh about 190-195lbs (88kgs) without gear. And I am looking at getting a 7.5kg/mm rear eibach spring and a .60kg/mm front springs with gold valves front and rear. I am sure this question has been asked many times but if you have any idea of whether that would be about the right weight springs or not I would appreciate it.

I will be setting the bike up for ADV riding and commuting - but happy to set it up more suited to dirt than blacktop.

And does anyone know what it would cost to get this done at HOEY racing (Australia)

Cheers,
TJ
I am about 20 lbs heavier than you and have similar plans for riding. I went with .70 fork springs and 8.1 rear spring, so I think you're about spot on. My suspension parts should be here next week so I have no experience with them yet.
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Old 12-16-2012, 09:57 AM   #71871
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Quote:
Originally Posted by Mambo Dave View Post
Speaking of suspension, I'd like to hear from those who have cut their fork springs to gain some stiffness.

I've got to imagine that since the extra range of the springs is being substituted for firmness, that it becomes a tiny bit harsher for a given outcome than would buying new springs that are just as long as the stock ones, but made thicker.

Anyway, I can't quite see how cutting my springs to save money would be such a bad idea since I'm not creating a Baha racing machine here. The last bike I bought springs for showed me that aftermarket springs were often shorter, anyway, than the originals.
Why not just add preload, by using longer spacers? Keep your springs intact. It's easier to revert back to stock or to sell.
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Old 12-16-2012, 10:05 AM   #71872
Mambo Dave
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Originally Posted by Kommando View Post
Why not just add preload, by using longer spacers? Keep your springs intact. It's easier to revert back to stock or to sell.
Selling isn't a worry - most americans are frickin heavier than I am, so they'll need the extra stiffness.

I've read up on suspension enough to believe that preload is preload - it's either set right or it isn't. While it may change the spring rate a fraction of a percentage, it really isn't supposed to, and it doesn't make up for spring rate changes.

Adjusting preload with the end-goal of a quick and dirty rate change is sort of ... well, it just doesn't seem right.
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Old 12-16-2012, 11:56 AM   #71873
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Quote:
Originally Posted by Mambo Dave View Post
Selling isn't a worry - most americans are frickin heavier than I am, so they'll need the extra stiffness.

I've read up on suspension enough to believe that preload is preload - it's either set right or it isn't. While it may change the spring rate a fraction of a percentage, it really isn't supposed to, and it doesn't make up for spring rate changes.

Adjusting preload with the end-goal of a quick and dirty rate change is sort of ... well, it just doesn't seem right.
On progressive-rate springs, like the DR's stockers, a change in preload changes the spring rate.
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Old 12-16-2012, 11:58 AM   #71874
motolab
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Quote:
Originally Posted by LexTalionis View Post
Have over 18k miles (you can do the conversion math to kilometers) on my OEM carb, haven't opened it up since I adjusted the fueling at around 500 miles by installing a washer and backing out the A/F screw.
As shimming the needle clip preloads the slide spring beyond standard, it results in lowering the slide rather than raising the needle (except when the slide is against the stops). I would not shim the needle clip unless the goal is actually to lower the slide for a given intersection of throttle angle and rpm. Note that the additional preload from shimming the needle will also make the slide come off the stop at a later point in terms of rpm and throttle position (i.e. more velocity will be required to get it to come up off of the stop).

The most proper way to refer to the idle mixture screw (aka pilot screw) on a BST carb is as a fuel screw, as it does not adjust air and fuel simultaneously. There are things called air screws on carbs where you adjust the idle mixture by changing the quantity of air being bled into the pilot circuit. The reason this is important is that a fuel screw makes the idle mixture richer by screwing out and leaner by screwing in, whereas an air screw makes the idle mixture richer by screwing in, and leaner by screwing out. Fuel screws are usually on the downstream side of the slide, and air screws are usually on the upstream side (although I have seen occasional exceptions).

Regards,

Derek
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Old 12-16-2012, 12:05 PM   #71875
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Quote:
Originally Posted by blackcap View Post
seems i keep tearing through slides, slide guides and emulsion tubes on the BST. starting to feel like this set is done after only about 10 000km and the set before that was only about 20 000km
Have you been increasing the lift hole area, or leaving it stock? I assume this is a single lift hole model? Make sure you are preventing the ingress of dirt through the carb vent (the 1/2" {~13mm) steel elbow on the back of the carb, just under the diaphragm).

Regards,

Derek
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Old 12-16-2012, 12:15 PM   #71876
SprintST
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Another chain question

Hi guys,

Quick question. I'm on the road in southern Argentina and can't replace my chain for a few days. I adjust at the tightest spot, of which there shouldn't be one after only about 10k kms. When I'm on the loaded bike the chain is quite loose. Better loose than tight, I know, but does anyone have any suggestions on other courses of adjustment? When should the damn thing be adjusted? Loaded? Loaded, with my fat ass on it as well? Unloaded? On side stand? Upright under its own weight? Rear wheel off the ground?

Will a sticky point chain ever "unstuck"? It's at 4+2 on the adjuster cam now.

It's all cleaned up, lubed and awaiting your collective wisdom.

Cheers!
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Old 12-16-2012, 01:49 PM   #71877
motolab
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Quote:
Originally Posted by blackcap View Post
i dont know anything about the TM40 or how it operates.
Slide carbs will always have a loss in bottom end to lower midrange of the rpm range at the larger throttle openings because the air velocity (and therefore the quality of the metering) is proportional to the engine rpm and inversely proportional to the throttle opening. Slide carbs require you to learn throttle control. When tuned properly (I say "tuned properly" because it is possible to mask many problems with an overly rich mixture), you cannot open the throttle to WOT or near WOT suddenly from low rpm without significant hesitation (its even possible to stall the engine if you dont back off). A properly tuned accelerator pump will help this, but is not likely to completely mitigate the problem. On the other hand, CV carbs allow you to open the throttle all the way from low rpm and will pull smoothly when tuned correctly, because the height of the slide automatically attempts to maintain a consistent velocity.

The ability to open the throttle to WOT from low rpm without hesitation with a CV carb does come with a price, and that is in a comparative lack of responsiveness in those areas where the combination of throttle position and rpm does not cause too much of a loss in in intake velocity with the slide carb.

Another area where the CV carb has an advantage is in the ability to change the fuel delivery curve based on rpm via the needle shape. On a slide carb, you can add or subtract fuel via tuning a circuit responsible for a given throttle position, but you cannot change the shape of the delivery curve in terms of rpm. For instance, if you had a lean and a rich spot at different rpm at a certain throttle position, you could fix the lean spot while making the rich spot even richer, or you could fix the rich spot while making the lean spot even leaner. You could not fix both. Unfortunately, these types of scenarios happen quite frequently.

The throttle pull on the TM40 is also quite a bit heavier than on the BST40.


Regards,


Derek
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Old 12-16-2012, 01:54 PM   #71878
motolab
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Quote:
Originally Posted by Kommando View Post
On progressive-rate springs, like the DR's stockers, a change in preload changes the spring rate.
If the fork is far enough into the travel, the rate becomes the same as it was again.

Regards,

Derek

motolab screwed with this post 12-16-2012 at 02:05 PM
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Old 12-16-2012, 02:04 PM   #71879
motolab
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Quote:
Originally Posted by Mambo Dave View Post
I've got to imagine that since the extra range of the springs is being substituted for firmness, that it becomes a tiny bit harsher for a given outcome than would buying new springs that are just as long as the stock ones, but made thicker.
It makes no difference whether the rate is achieved with a shorter spring or bigger wire. Rate is rate. The only time you have to worry about a shorter spring is if the travel is so long that that the spring could become coil bound before the fork would normally bottom (not a common issue).
Quote:
Anyway, I can't quite see how cutting my springs to save money would be such a bad idea since I'm not creating a Baha racing machine here. The last bike I bought springs for showed me that aftermarket springs were often shorter, anyway, than the originals.
Just make sure you cut them evenly so the rates are the same, and that you close the ends and grind them so they are square and flat when you are done.

Regards,

Derek
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Old 12-16-2012, 02:36 PM   #71880
Mambo Dave
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Quote:
Originally Posted by motolab View Post
It makes no difference whether the rate is achieved with a shorter spring or bigger wire. Rate is rate. The only time you have to worry about a shorter spring is if the travel is so long that that the spring could become coil bound before the fork would normally bottom (not a common issue).Just make sure you cut them evenly so the rates are the same, and that you close the ends and grind them so they are square and flat when you are done.

Regards,

Derek
Thanks man - like, evenly within... say... 2mm or 4mm? or are we talking precise here?

I take it the PVC i should buy will be schedule 40... anyone happen to know the size?
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