Two more BK mods completed!!

28 replies to this topic
  • Jason_in_KC

Posted September 25, 2001 - 05:18 AM


Well....hell w/the cough..I took the beast out yesterday to an open loamy dirt area where new houses are being built. WOW! 1st-3rd gear it is hard to keep the front wheel down. I have the 12oz flywheel on and that extra traction is amazing along w/the mod. I did a 2nd gear start and carried the front wheel until I shifted to 3rd and continued w/the wheel about 6inches off of the ground. Putting around in 2nd(idle is set higher now)just grab a handfull and up she comes. Easy adjustments can be made to the ac pump screw and delay screw if you leave the black cover off for some test runs, taking the coil out of the way helps also...just don't forget to put it back on! Too cool.

  • Terry_in_Reno

Posted September 26, 2001 - 09:25 PM


I found with making the mod I needed to adjust the idle up just a few RPM to help. It is supposed to be 1600 to 1800 RMP.

What I also found on mine was that the spray was delayed so that it really was effecting the mid band. When adjusting the timing of the squirt to match with the slid openning the pilot circuit became richer than before. I turned the pilot fuel screw in to solve the cough.

Then I lowered the clip position one spot to give the mid back the fuel it lost when I retimed the squirt. This may not be necessary in all cases. The squirt was about 2.5 second on mine before, so it was getting a healthy dose of fuel in the mid range.

BK had stated the mid and upper ranges needed to be richened up with this mod. It seems to make sense if you cut the duration and time of the squirt then you will need to compensate in the area effected. Just my 0.02

  • dirtdad

Posted September 26, 2001 - 09:51 PM


Terry, which direction did you go on the timing screw to get it started sooner? I've done the mod but haven't fiddled with the timing of the squirt. It's missing the slide but coming on much later as you stated.

00 YZ426F
01 TT-R125L (my son's)
74 Hodaka Super Combat(gone but not forgotten!)

  • Hick

Posted September 26, 2001 - 10:37 AM


Clockwise delays the squirt, counterclockwise advances it.

I think. Let me talk myself through it:

The screw points rearward, screwing it in then serves to lift the actuating arm and rod. So when you open the throttle then it will take a bit longer for the rod to contact the diaphragm (can we all spell that correctly now, hmmm??) and begin operating the pump.

Yep. In delays, out advances.

Hope this helps.

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  • Terry_in_Reno

Posted September 26, 2001 - 12:11 PM


Hick's got it.

I found the timing was more involved in the cough than the duration. The duration had more involvement with the crispness of the responce.

I've always have tinkered with tuning, so I didn't find it too difficult to find the right setting, but if talked to several that wanted some help after I described the process. Then again maybe its my way of discribing that gets that responce.

  • dirtdad

Posted September 26, 2001 - 12:16 PM


thanks guys.

00 YZ426F
01 TT-R125L (my son's)
74 Hodaka Super Combat(gone but not forgotten!)

  • scottzx7rr

Posted September 26, 2001 - 09:02 PM


Yeah Reed. I have created a email group for local Riders in KS/MO area if you want to join just go to the site and subscribe. The members get together and have rides every so often.

Scott #410
Some Fear Racing "Cause if you don't have any you ain't going fast enough"
'99 YZ400F(Coming to a Theater near you soon)
'92 ZX-7R and '97 ZX-7RR
"Doesn't hurt till the bone is exposed"
"When cut do you bleed green? I do!"

  • bbeakley

Posted September 30, 2001 - 06:06 AM


I did the mod yesterday and had a little trouble tuning the squirt duration. After making an adjustment, I'd whack the throttle open several times to check the duration and found that duration changed each time. Is it supposed to be consistent each time? It usually became shorter. I was wondering if the pump had to reload with fuel and I wasn't allowing it time to do this. I'm going to go ride it today and see how it does after it's warmed up.

  • bbeakley

Posted September 30, 2001 - 12:27 PM


Well, throttle response is much crisper. I still get a bog if I'm at low rpm and open it up really fast, but I think a little more tuning with the delay screw and duration can cure that. If I just roll the throttle on, it doesn't bog. One side note, my decel backfiring has gone away completely. I'm not sure I understand that, but hey, I'll take it. Thanks to BK for the ingenious fix and Garrett for posting the pics and procedures.

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