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Old 01-09-2013, 08:14 PM   #72676
procycle
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Originally Posted by motolab View Post
The validity of these statements depends upon whether the hesitation is in the 1/16-1/8 or the 1/4 opening range.
No. My statements are valid because this is the experience DR650 owners have when they decide to increase the pilot jet size (which was probably a quick easy fix on their last motorcycle). Instead of solving the hesitation they get a rich bog. My point is that using the pilot jet to try to cure the DR650 off idle leanness is running down the wrong path.

My statement is specific to the DR650 not a general observation about motorcycle carburetion and based on reading forum posts here and elsewhere regarding what actual owners have done to their actual bikes.
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procycle screwed with this post 01-09-2013 at 08:51 PM
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Old 01-09-2013, 08:14 PM   #72677
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Originally Posted by procycle View Post
Yes, yes, but you may be the only DR owner who has done that. Most expect a bigger pilot jet will cure a lean hesitation which is actually due to the needle. They end up with a rich bog off idle followed by the same lean hesitation they started out with.
It's cause I is smart.

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Old 01-09-2013, 08:17 PM   #72678
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Originally Posted by motolab View Post
The galling in the middle (that is where the pin runs in the small end of the rod) indicates an oil film failure, which is usually caused by detonation.
And you can be sure there is matching galling in the small end of the rod. Any repair that does not include replacing the connecting rod is going to have limited life/reliability.
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Old 01-09-2013, 08:22 PM   #72679
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Originally Posted by opium89 View Post
For the record, I did plug the purge port along with the vacuum port on top normally used for the stock petcock.
Is the vacuum port o-ring in place underneath the diaphragm cover?
Quote:
The only other hoses coming off the carb now are for the breather and there's one other one right below it that isn't attached to anything and runs up under the seat alongside the breather. I am not really sure of it's function.
The smaller one on the right is a float bowl vent.
Quote:
I am however aware of the fuel screw and it's function, just wanted to be clear to everyone what I was referring to.
Accurate terminology helps with clarity. Inaccurate, not so much.
Quote:
I will also take a very close look around the airbox and maybe go as far as to remove it and the air boot and makes sure there are no leaky-leaks anywhere.
Vacuum leaks will generally be on the downstream side of the butterfly, which the airbox and airbox boot don't really have anything to do with. What method have you been using to detect leaks?
Quote:
My initial guesswork has evolved around the throttle at 1/8 where the hesitation is taking place. This is really why the talk about the pilot jet has been bothering me.
The high idle and rise in rpm when the fuel screw is opened indicate that the pilot jet is not likely to be at fault, or at least not solely.

Regards,

Derek
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Old 01-09-2013, 08:27 PM   #72680
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Originally Posted by procycle View Post
And you can be sure there is matching galling in the small end of the rod. Any repair that does not include replacing the connecting rod is going to have limited life/reliability.
What? You can't just change the bushing in the small end?
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Old 01-09-2013, 08:48 PM   #72681
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Originally Posted by Emmbeedee View Post
What? You can't just change the bushing in the small end?
No. There is no bushing. That's pretty standard for Japanese motorcycles for at least the last 30-40 years. The pin runs directly in the rod.
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Old 01-09-2013, 08:51 PM   #72682
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Originally Posted by procycle View Post
No. There is no bushing. That's pretty standard for Japanese motorcycles for at least the last 30-40 years. The pin runs directly in the rod.
Too bad. My old BSAs, Triumphs and Ducatis had 'em.
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Old 01-09-2013, 08:53 PM   #72683
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Originally Posted by Emmbeedee View Post
Too bad. My old BSAs, Triumphs and Ducatis had 'em.
Yeah, and those bushings were good for 10 maybe 20 thousand miles. There's a reason you don't see modern iron built that way anymore.
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Old 01-09-2013, 08:54 PM   #72684
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Originally Posted by procycle View Post
Yeah, and those bushings were good for 10 maybe 20 thousand miles. There's a reason you don't see modern iron built that way anymore.
Now that you mention it... I just remembered why I'm out of Vintage bikes. I prefer riding.
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Old 01-09-2013, 08:56 PM   #72685
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Originally Posted by procycle View Post
No. There is no bushing. That's pretty standard for Japanese motorcycles for at least the last 30-40 years. The pin runs directly in the rod.
But, the end can be re-honed. Chances are it is on the small size and anyone who actually does rods wouldn't think twice about puting .0002-.0003" more clearance on the pin. And it will not hurt the life of the rod. It is a common and proven practice.

I don't own a $15,000 rod machine because reconditioning rods reduces "life/reliability". Matter of fact every NEW rod we get gets honed to our specifications- We have NEVER had a rod or pin failure in 20 years. I think that should count for something.

And wouldn't say that is from detonation until I actually measured it. Detonation does cause galling, but not normally there. It usually causes the hole to oblong in the up/down area.
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Old 01-09-2013, 08:57 PM   #72686
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Originally Posted by procycle View Post
Yeah, and those bushings were good for 10 maybe 20 thousand miles. There's a reason you don't see modern iron built that way anymore.
Once again wrong. MOST modern cars have bronze bushing rods now: Chevy LS motors, Ford Modular motors, Honda motors to name a few...
And in motorcycles the gsxrs, and busas.


Try again.

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Old 01-09-2013, 09:06 PM   #72687
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Quote:
Originally Posted by motolab View Post
Is the vacuum port o-ring in place underneath the diaphragm cover?
Yep, and it's new.

Quote:
Originally Posted by motolab View Post
The smaller one on the right is a float bowl vent.
Thank you for clarifying.

Quote:
Originally Posted by motolab View Post
Vacuum leaks will generally be on the downstream side of the butterfly, which the airbox and airbox boot don't really have anything to do. What method have you been using to detect leaks?
Agreed. In my days as an auto mechanic, I used to spray brake cleaner around the suspect area(s). Temporary idle up generally is indicative of a leak. I will take a closer look at and around the top cap.

Quote:
Originally Posted by motolab View Post
The high idle and rise in rpm when the fuel screw is opened indicate that the pilot jet is not likely to be at fault, or at least not solely.
Agreed.
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Old 01-09-2013, 09:10 PM   #72688
gofast1320
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jacked up petcock

May have been some funk in the carb needle seat. I changed the petcock out for one off of the OEM tank. Filled it with fuel and it did not leak. Hooked up the hoses and cranked it and started it up. Rode it around in the woods 2 miles and then back and forth up and down the driveway getting it up to 50 and backing off, then going again. Its running fine and no gas is running out of it. Thanks for all the tips and advice.Thinking about taking the carb off and rebuilding it makes me sick to my stomach.
Quote:
Originally Posted by motolab View Post
As it is not possible for the carb to overflow without fuel getting past the float valve, leaving the petcock in the PRI position cannot be the sole cause.

Regards,

Derek
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Old 01-10-2013, 05:00 AM   #72689
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Quote:
Originally Posted by motolab View Post
The galling in the middle (that is where the pin runs in the small end of the rod) indicates an oil film failure, which is usually caused by detonation.
Thanks! Wouldn't detonation leave other visible traces/marks as well? Also I don't know, what could possibly cause detonation in such a low compression engine?



Quote:
Originally Posted by procycle View Post
And you can be sure there is matching galling in the small end of the rod. Any repair that does not include replacing the connecting rod is going to have limited life/reliability.
Quote:
Originally Posted by Mongle View Post
But, the end can be re-honed. Chances are it is on the small size and anyone who actually does rods wouldn't think twice about puting .0002-.0003" more clearance on the pin. And it will not hurt the life of the rod. It is a common and proven practice.
Guys, this sounds very bad. Getting the rod out of the engine to have anything done to it would be major PITA for me, I really wasn't planning on splitting the crankcase (plus I don't have the special tools for this job).
I for sure will check how the small end looks, as soon as I have a chance.
Mongle, you mean even being given brand new stock rod, piston and pin, you would re-hone them to alter the stock clearances between the new items?
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Old 01-10-2013, 07:06 AM   #72690
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Quote:
Originally Posted by Mongle View Post
Once again wrong. MOST modern cars have bronze bushing rods now: Chevy LS motors, Ford Modular motors, Honda motors to name a few...
And in motorcycles the gsxrs, and busas.


Try again.
Actually you are wrong, can't speak for cars but I have rebuilt a Busa and I know for a fact it does not have bushings at the piston pin. It does have BEARINGS (OK, they're really bushings but that's not what they're called) where the con rod connects to the crank but you would have to be kinda of dense not to understand what he was talking about.
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