Author Topic: Racer Resurrection  (Read 70576 times)

0 Members and 1 Guest are viewing this topic.

Offline al_pritchard

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 107
Re: Racer Resurrection
« Reply #240 on: May 10, 2019, 09:13:22 AM »
The needles are 4J6, and the clip is in the 2nd position (second from the top)

Going to re-set up the carbs and if the weather holds give it a go later today.
Al Pritchard
Highlands, NJ

BS175 Racer

Offline bsracer

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 333
Re: Racer Resurrection
« Reply #241 on: May 12, 2019, 01:18:05 PM »
I tried a 4J6 needle out at Willow last month.

200 main
35 pilot
4J6 with the clip in the top groove

Too rich off throttle (3/4 to WO) and bike would bog

went to a 190 main and 30 pilot with no real difference

went to a 4J15 needle which is leaner with clip in the bottom groove and a 25 pilot with the screw turned in to about a 1/4 turn out

I was running a 4DH7 needle prior which is leaner still with clip in the bottom groove.

I use to run 4D20 needles which are really fat (lean) but the clips for those are bigger diameter for the relief in the slides I use and the needle would be raised a bit.

paul

Offline SR-175

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 86
Re: Racer Resurrection
« Reply #242 on: May 20, 2019, 07:23:09 AM »
Hi Paul,

Could you take a pic of the various needles you have.

In the attached pic, the one on the left is a 4J5, the one on the right has no markings. It came as part of a VM22 repair kit I bought for a Kawasaki A1.

I am using VM-22's off a Kawasaki A1 250.

Thanks .. ray

Offline SR-175

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 86
Re: Racer Resurrection
« Reply #243 on: May 21, 2019, 10:25:32 AM »
Hi Paul, Al,

After digging through parts here I found a few other needles to compare. It seems the needles in the Kawasaki A1 250 carb kits are close too the 4J6's.

Note the main needle jet - the centre hole that needle jet slides in is smaller than the 2.5 mm diameter of the needles ??...

ray


Offline al_pritchard

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 107
Re: Racer Resurrection
« Reply #244 on: May 21, 2019, 10:49:06 AM »
Hi Ray

I was wondering what needle came with my rebuild kit. Guess it's a 4J6.

Was not particularly happy with the quality of the kit, overall. Some of the jets still had burs from machining in them. Decided to only use the gasket and put the rest of the shelf.

In the image below (click image for larger view) is the needle from the Kawasaki A1 kit I got. Next to a 4DH7, 4F15, and a 4J11. That 4J11 looks so short - no wonder it's so much richer than the others.


Al Pritchard
Highlands, NJ

BS175 Racer

Offline vinny g

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 53
Re: Racer Resurrection
« Reply #245 on: May 21, 2019, 04:53:44 PM »
Hi Al. From memory I ran 4D3/4 needles in N size jet holders/needle jet. You can normally fine tune on the clip but certainly you won't need much richer (thinner) I'd look for around a 4D3 in a N4 holder. Incredibly important to get this there or thereabouts as you can change main jet all you want...it won't make a difference unless you're close with needle/jet combo. When I ran 22mm's I used slot head jets.. 110-130. These are diametric.. (100 is 1mm) With 28mm's I run 200-210-220 hex head. These are flow rated.

Quite a while since I ran 22mm's but I've probably got it written down somewhere and will dig it out. Certainly though...N size needle jet.

Cheers, Vince

Offline SR-175

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 86
Re: Racer Resurrection
« Reply #246 on: May 22, 2019, 02:04:48 AM »
Hi Al .... all,

It's a pity the kits are not made a bit better and marked. Even a note in the bag would help ? We reproduced these to blah, blah, spec ...

Yes, found burrs & swarf. The air screw & spring measured up ok ??.... and the gasket.

A can of worms has been opened up on what needle jet to use ?

ray

Offline bsracer

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 333
Re: Racer Resurrection
« Reply #247 on: May 24, 2019, 11:25:29 AM »
I'll try and get some pics of the needles I have in the next day or two.


paul

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 873
Re: Racer Resurrection
« Reply #248 on: May 25, 2019, 08:08:18 AM »
          Here's another tuning guide I found useful when setting up the GTO.  Again aimed at the Kawa triples but they use similar Mikuni carbs to our Bridgestones. Lots of stuff you will already know but has some good basic info on which way to go with jet/needle sizes . Also warns against the use of non Mikuni overhaul kits as Al/Ray point out.
             https://www.3cyl.com/mraxl/manuals/carbtune/carbtune.htm

          See the section on ''Effect of jetting variables'' near top and the tables right at the bottom which show dimensions of various series 4 needles and needle jet sizes. Might help to identify those unmarked needles although would require measuring to a 1000th of a mm!!
        Hope this helps, a can of worms indeed.                                               Brian.
« Last Edit: May 25, 2019, 09:16:29 AM by BRT-GTR »
Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline SR-175

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 86
Re: Racer Resurrection
« Reply #249 on: May 26, 2019, 03:18:48 AM »
Hi Brian,

Very helpful lead !!.... thanks ... ray

Offline al_pritchard

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 107
Re: Racer Resurrection
« Reply #250 on: June 04, 2019, 09:15:32 AM »

And it's alive. No, it's not Déjà vu. If you are on the Bridgestone Facebook group you may have already seen this. But I thought I should upload it, and record the carb settings, and next steps.

Set Up
Pilot Jet: 20
Main Jet: 230
Air Screw: 1/2 turns out
Float: 25mm
Fule: 112 octane / VP C12
Oil: 28:1 / Castor 927

Did't do any carb tuning yet. Just wanted to get the first heat cycle in. A couple of notes, and things to do. She doesn't idle yet - not unexpected. I didn't take any time to start to work that out. She also stumbles pretty hard as you open the throttle.

I suspect as I start to get the idle set, it will help the 1/8 open throttle stumble. If I understand the tuning it's a combination of the height of the throttle valve and the needle jet.

And thats for that link Brian. It's helping me better understand how the carb works, and how to go about tuning it in.

Click image to view video
Al Pritchard
Highlands, NJ

BS175 Racer

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 873
Re: Racer Resurrection
« Reply #251 on: June 04, 2019, 02:41:22 PM »
            Congratulations on getting her running.   Here's how I went about getting the carbs right.
         Start at the bottom (idle) and work up the range to top end (main jet) with tuning. At 1/8 throttle she is on the top end of the pilot circuit.
             Suggest winding the idle screws up to raise the slides to a point where she will idle. Then adjust the airscrews, to give highest idle speed. Do one pot at a time, removing plug from other pot but ground the plug of the disabled pot on the cylinder head to avoid coil damage. Bear in mind this is a race tuned engine, it may not idle like a swiss swatch !!
   
           Ideally Mikuni say airscrew should be between 1-2 turns open. Less than 1 turn - pilot jet too small, more than 2 turns - pilot jet too big.  After adjustments you need to back off the idle screws equal amounts to give required idle speed.
             If a cylinder doesn't respond to the airscrew, the screw may have been overtightened at some time expanding its seat in the carb body (quite common in my experience). Not much you can do about this. With a relatively high idle speed the adjustment may be outside the range of the pilot circuits in which case set the best, reliable idle you can achieve.
              Once you are happy with the idle, move up the range . I wouldn't worry too much about the slide cutout at this stage, the factory went for a rich setting (small cutout), it may be OK. Come back to it if you can't get rid of the stumble. 
             Needle clip position/needle size/needle jet are the next items to play with, good luck.
« Last Edit: June 19, 2019, 07:38:20 AM by BRT-GTR »
Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline SR-175

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 86
Re: Racer Resurrection
« Reply #252 on: June 17, 2019, 10:33:45 AM »
Hi Al,

You can also toss the air screw into the bin. After closer inspection and trying to use it I have found the originals to be better. The tip diameter is not the same by about 0.15 mm.

Offline al_pritchard

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 107
Re: Racer Resurrection
« Reply #253 on: July 08, 2019, 03:57:02 PM »
Yea, I didn't use air screw ether. Total crap!


Spent a little more time with her over the long holiday weekend. The goal was to get her idling, and take a quick run around he block

Got her running, and idling well enough - more on this below. And a good heat cycle in the engine.

But I couldn't get her to go anywhere. The minute you started to let out the clutch, she died. No matter how hi you held the RPMs, the moment you put a load onto engine she bogged out and died.

Back up on the bench. A quick pressure test told the story. 45lb of compression! Thats all she can muster from each cylinder. Pulling the heads you can see the oil drops outside the o-ring. So at least that explains why she can't move under her own power.

I think I cut the o-ring grove to deep, or to wide for the o-ring. So I'm going to take a little more off the head, and see if I can get her to give me something a lot better on a compression test.

The leak down test didn't show a problem. I guess because the leak down was about 4 or 5 lb. and the o-rings are holding at least 45lb.

Would be interested in what others are seeing from a pressure test.





Al Pritchard
Highlands, NJ

BS175 Racer

Offline al_pritchard

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 107
Re: Racer Resurrection
« Reply #254 on: August 30, 2019, 05:45:18 PM »


So, I am at a complete loss. Any thoughts would be welcome.

Got a new - to me - set of heads in the other day. With the plan to cut them down and run stock head gaskets.

Since  was going to run a stock head gasket, I cut the heads a little more than the last set. These come out at 7.1cc. I figure the head gasket is good for 0.2 or more.

Buttoned up the engine, and gave her a good push. Fired right up, and fiddled with the idle a little. Once she was warm, she had no problem revving up. But she still won't make power. Tested with the engine warm, and I only get about 90 lb of presser. I am at a complete loss.

Top End
Ring Gap: 0.015" / 0.38mm
Deck Heigh: 0.040" / 1.01mm
Head Volume: 7.1cc
Base Gasket: 0.031" / 0.79mm
Head Gasket: 0.039" / 1.0mm
Head bolts torqued to 140 in lb.

*The head gasket crushes down to about 0.024" / 0.60mm


Stock 11.3cc on top
Cut 7.1cc on bottom



NOS Head Gaskets - Thanks Richard!
Al Pritchard
Highlands, NJ

BS175 Racer

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 873
Re: Racer Resurrection
« Reply #255 on: August 31, 2019, 07:02:24 AM »
   Al,
        Initial thoughts,   
     Use annealed copper head gaskets, more up to the job, much better seal than alloy, and may allow reduction in head nut torque reducing distortion.  Your head nut torque seems low, what is BS standard figure ? haven't checked.
        Bog/lack of power may be due to weak mixture, try 1) turn in airscrews 1/4 turn at a time and test 2) if airscrews less than 1 turn out go to next bigger pilots 3) raise jet needles. Does she bog then go or bog then die. I found if airscrew was too far out with smaller pilots , she would bog on takeoff. Are plugs wet or dry after a test.
        90 lb pressure, seems low, not sure, rings need to bed in? piston clearance? Seems to be a noticeable visual difference on opposite sides in piston land clearance on left pot, bottom photo but could be camera parallax error or shadow. What's your compression ratio with new heads.                                                                         Brian.
« Last Edit: September 02, 2019, 07:12:45 PM by BRT-GTR »
Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline bsracer

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 333
Re: Racer Resurrection
« Reply #256 on: September 02, 2019, 12:23:21 PM »
Where is the clip position on the needles? And what needles do you have in the carbs? This is how mine first ran until we went to an extreme to find it was too rich. If I remember the mixture screws were barley cracked. You may have to put the clip in the top groove depending on the needle. 4D4 or 4D20 are fat taper. You may also want to drop to a 210 or 200 main to start. Are the discs cut 10 and 10?

paul

Offline al_pritchard

  • Trade Count: (0)
  • Full Bridgestone Member
  • ***
  • Posts: 107
Re: Racer Resurrection
« Reply #257 on: September 03, 2019, 08:53:31 AM »
Hey Brian,

The deck heights match cylinder to cylinder. In the photo above the "left" (right in the photo) cylinder has the head gasket on, and the other doesn't. Don't know the exact compression ratio with the new heads. I'll assume it is similar to the old heads. Old heads were cut to 8cc, and were set up for an o-ring. The new heads are cut to 7.1, and use a stock head gasket. I'm assuming the

Uncorrected Compression Ratio: 13:1
Trapped Compression Ratio: 7:1

Going to start over with tuning, beginning with the air screw as you suggest above.

Hey Paul,

The carbs are currently:

Needle: 4F15 - clip in the 2nd position (from the top)
Pilot: 25
Main: 220
Fuel: 28:1
Timing: 2mm / 20°

Going to fiddle with it a little more this afternoon. I'll update with any progress.
Al Pritchard
Highlands, NJ

BS175 Racer

Offline BRT-GTR

  • Brian
  • Trade Count: (0)
  • Master Registered Bridgestone Member
  • *****
  • Posts: 873
Re: Racer Resurrection
« Reply #258 on: September 04, 2019, 08:37:19 AM »
    Hi Al,
    We may be at cross purposes here, calculating your potential max cylinder pressure, I get 154psi but actual figure will be lower. 90psi suggests something is wrong. On the bottom photo, left cylinder,  there seems to be a much bigger cyl/piston gap on one side of piston but maybe camera or shadow/reflection.
   Good luck with the tuning, there's a lot of variables to play (Fiddle  ;D) with. I've been fiddling with my carbs for months. I have seen another tuning article which suggests getting the pilot jet and main jet settings ( that assumes she will pull through the  mid range)  sorted first because they have little or no effect on mid range running. Then play with the needle clip position and/or needle jet  size.                                                            Brian.
« Last Edit: September 04, 2019, 05:25:44 PM by BRT-GTR »
Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline bsracer

  • Trade Count: (0)
  • Expert Registered Bridgestone Member
  • ****
  • Posts: 333
Re: Racer Resurrection
« Reply #259 on: September 05, 2019, 11:00:22 AM »
My bike is at work so I'll look at the carb settings later today. If the 4DH7 is the leanest needle you have, I would try that with the clip in the top groove. Try a 20 or 22.5 pilot, and put in 200 main jets if you have them. I would turn the mixture screws all the way in and just crack them open between a 1/8-1/4 turn. If you get it running and idling you may have to turn in the mixture screws in to get it to rev freely.

paul

 


Gallery


Views:19
Comments (2)
By: Detecable

Views:16
Comments (0)
By: rwgibbon

Views:14
Comments (0)
By: rwgibbon

Views:18
Comments (0)
By: rwgibbon

Classifieds

Gtr
Date: 11/23/2019 10:27 am
Time Left:
GTR handlebars
Date: 11/17/2019 01:05 pm
Time Left:
GTR
Date: 10/27/2019 03:34 am
Time Left:
'71 BS350, Illinois

Price: $0.00
Date: 10/24/2019 05:24 pm
Time Left:

Recent Downloads added

!75 Wiring Diagram - Color Coded
Rating: (None)
Filesize: 136.77KB
Date: February 27, 2019, 01:00:42 PM
11/01/1967 Factory Service Letter, RH shift/LH Brake conversion

Rating: (None)
Filesize: 92.56KB
Date: August 03, 2018, 02:49:08 AM
11/01/1967 Factory Service Letter, RH shift/LH Brake conversion

Rating: (None)
Filesize: 142.24KB
Date: August 03, 2018, 02:44:36 AM
350 GTR Wiring Diagram
Rating: ***
Filesize: 8604.23KB
Date: July 29, 2018, 12:29:25 PM

Powered by EzPortal