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Maj0r

Drilling holes in slide.

8 posts in this topic

Greetings.

I have a 2000 XR600 that I'm exetremely happy with, except for 1 common problem..

The "Bog" just off idle is a real pain in the ass for me. I ride road and dirt and it really irks me that I can't get the power on smoothly at say, a roundabout or up a steep hill between narrow trees etc.

I've read here somewhere that a 2 mm hole drilled in the slide 12 mm from the top of the slide will help get rid of this problem. I'm a printer, not a mechanic, so my understanding of how a carby works is limited at best. Can someone explain in simple terms how this vacuum process works and will a 2mm hole actually help and why?? Does the positioning of the hole around the circumference of the slide matter and why? What does "shim" the needle mean??

Thanx in advance.

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G'day, I once read about this "fix" in an aussie magazine. Although I've never tried this, I read that it helped a little bit but didnt cure the problem which is common to all XR600's with a single carb ('88 on). In my opinion, there's nothing you can do for this "stickyness" of the throttle, it's just a character trait of the XR6 and you learn to live with it. However, pull apart your throttle assembly and lube the cables and clean everything- this can help as the cables have often got dirt/rust in them which magnifies the problem. You mention that your bike "bogs", it may stall at low revs (this is common with all large singles with a large bore carb, this shouldn't occur and maybe you need to check and clean everything in the carb and maybe check the jetting.

Good luck!

Mark.

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Ta Mark. Will do.

Not sure if "bog" is the correct term. The power is either not there or it is. Seems no way to gently bring the power on other than ride the clutch..

But I've lived with it for a while and other than get a flat slide carby (too much) or a postie bike I should stop bitching and get on with it.

If your ever bringing your bike up to Sydney give us a yell, theres some nice tracks at the foot of the blue mountains...

Ta again.

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G'day, I once read about this "fix" in an aussie magazine. Although I've never tried this, I read that it helped a little bit but didnt cure the problem which is common to all XR600's with a single carb ('88 on). In my opinion, there's nothing you can do for this "stickyness" of the throttle, it's just a character trait of the XR6 and you learn to live with it. However, pull apart your throttle assembly and lube the cables and clean everything- this can help as the cables have often got dirt/rust in them which magnifies the problem.

Keeping it clean and slippery as possible and keep throttle and cables lubed definitely helps. I never tried the drilling trick either. Another thing that helped some was taking a turn or two of preload out of the throttle return spring.

fwiw, the problem annoyed me so bad that it came down to - replace the carb or replace the bike. For < $200 USD I got a non pumper TM40 and throttle, and am glad of it. The bike deserved it.

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I have an XR650L which has a similar carb. The air rushing through the carb under the slidse causes a vacuum, and the holes in the slide allow the vacuum to suck the air out from above the slide, pulling the slide up. To a certain degree, enlarging the passage or increasing the number of passages will aloow the slide to be sucked up quicker, opening the throttle more quickly.

The XR650L stock had crappy throttle response, and there's a fix for this model:

drill the 2 holes in the slide out to 5/32 inches to speed up the throttle opening,

shim the slide needle up by 0.030 inches to slightly richen the mixture,

rejet the carb slightly richer. Lean jetting will kill the throttle response.

The principles that apply to the XR650L will apply to anything with a vacuum carb.

-Dave

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Your L carb is not like the R carb at all unless you've replaced it. Offroad XR's have the type of carb where the slide is raised directly by the throttle cable.

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I'm a printer, not a mechanic, so my understanding of how a carby works is limited at best.

It's like they say ingnorance is bliss. I understand the theory of carburetors, but not necessarily engineering behind them. Get a Clymer or a Honda service manual. I did and I've never worked on any m/c carbs before. I've r/r'd the carb twice, rejetted, and drilled & shimmed the slide with excellent results.

There are (3) or more circuits these CV carbs have to deal with. Idle, part throttle & wide open throttle (WOT). For the XRL this is critical.

Rejetting is necessary if you do any of the following:

1) Remove the airbox snorkel

2) Change to a high-flow air filter

3) Install an aftermarket pipe and/or headers

Drilling the slide & shimming the needle help the idle, low-end bog and throttle response throughout the RPM range. (check previous post from XRL_Dave for the why)

I didn't understand the how and the why, but I did know the what and the where. And with some help and encouragement from TT, and other the XRL groups, it all went really well. In fact, I've done more to this bike than I ever expected. All mods are well worth the effort and highly recommended.

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