Bridgestone Motorcycle Parts Discussion Board
Bridgestone Tech Talk => 350 Talk => Topic started by: BS Mechanic on February 08, 2017, 10:59:45 AM
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Here's an interesting slip of paper I just found in a small BS labeled plastic bag.
I believe it was included in the tool bag when I purchased my new 350 in 1968.
Looks like the bag originally held two #130 jets and this note.
I don't remember well enough to be sure though, that was a few years ago!!
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Living in Texas, I shall make note of this! lol
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I've always run 130's in AZ.
...bert
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Great find BS, nothing wrong with your memory, look after that scrap of paper. This maybe explains why the 130s never got to the UK. 80 degs F was never heard of back in the 1960s !!!!!! 70-75 was a hot summers day !! :(
We get 80+ now :D but I think the temperature reference was Rockford's covering their backsides in case of overheating problems.
This was shown in a Rockford Service letter, BSG-0062, dated 10-1-67, which stated the 140s were for break-in only and a set of substitute 130s were packed with the tool kit after Ser No. 16T1646. No mention of 80 deg F !! It also says with the 130s , the float level was 15/16'' and the needle jet clip should be in the second from bottom position. Where did all those 130 jets go ?
Brian.
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I wonder what happened to all of those 130s also. Of the 13 350s to come into my possession in recent years exactly four have had the 130s installed.
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Of the 6 sets in my possession, 5 have 130's and 1 (from Colorado) has 120's....
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Another thought, what about factory fitted idle jets? My bike had #30s in it and when I order NOS jets from RC #30s arrived yet the manual states 22.5, any thoughts guys, esp those with multiple bikes ;)
Ryan
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Hi Ryan, I checked a couple sets today and both had 30's vs. the 22.5's in them. So now, like you, I too am curious as to .... what's up? ;D
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There wa a post a while ago about it, stating they run better with 22.5s, but I'm yet to find a supplier for the odd thread sized jet (0.75 pitch vs 0.7)
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Ok, I decided to go ahead and check all 6 sets I have and all 6 have the 30's in them.
The manual says 22.5 is the standard. So that means either....
1 - 6 different previous owners changed them to 30's. (for whatever reason)
or
2 - The 22.5 is a misprint in the manual.
or
3 - 22.5 is correct in the manual, but maybe there was a service letter recommending they be changed to 30's. (again, for whatever reason)
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Of the eight or so used carbs I have had about 2/3's were #130's. I believe the NOS set had #140's. Hardy, take a look at Sudco #004-005 for pilot jets that fit. Double check my notes, but you should find a range of pilot sizes there.
- Bob
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Just curious, but how many people are actually running 22.5 idle jets?
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My riders have 22.5s. Needles all have clip in second from bottom grove. Everthing that I've seen with 30s was still running 140s with the needle clip clear in the top groove. Remember most of these bikes were sold by shops that were not dedicated bike shops and few people ever attempt to properly jet whatever they are riding. They get on, they start it, and it runs. They're happy.
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Both my Rockford's GTR/GTO (late) manuals state 30 as standard for the pilot jet, another can of worms!, which manual states 22.5 ?
BS service letter BS-0067 states '' The Bridgestone 350 GTR will operate quietly - even at idle (LOL)- and deliver maximum performance if it properly tuned ''. It stresses the importance of idle speed sync for smooth slow running. I am having limited success in syncing my GTO tickover so decided to do some research and found this guide on the Kawatriple.com site, which use similar Mikuni carbs :-
http://kawtriple.com/mraxl/carb/carbadj.htm (http://kawtriple.com/mraxl/carb/carbadj.htm)
Lots of good tuning advise in here. I notice it does say that if the air screw adjustment is outside of the range 1 1/4 to 1 3/4 turns open, the idle jet is too small or too big. Our starting point setting is 2 turns open ! OK, this advise may not be applicable to our engines due to the disc valve induction but did BS move to a smaller 22.5 idle jet on some machines or was it a dealer/user mod. ?
As soon as I have finished derusting the fuel tank and put some fresh juice in her, I will have another go at syncing the cylinders and let you know how I go on.
Brian.
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Both my Rockford's GTR/GTO (late) manuals state 30 as standard for the pilot jet, another can of worms!, which manual states 22.5 ?
It's on the Technical Data page in the service manual that is in the downloads. However, it's not listed in the same manual I have in my possession.....?????
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Ok, I decided to go ahead and check all 6 sets I have and all 6 have the 30's in them.
The manual says 22.5 is the standard. So that means either....
1 - 6 different previous owners changed them to 30's. (for whatever reason)
or
2 - The 22.5 is a misprint in the manual.
or
3 - 22.5 is correct in the manual, but maybe there was a service letter recommending they be changed to 30's. (again, for whatever reason)
Sudco has them, or did two years back.
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Ok, I decided to go ahead and check all 6 sets I have and all 6 have the 30's in them.
The manual says 22.5 is the standard. So that means either....
1 - 6 different previous owners changed them to 30's. (for whatever reason)
or
2 - The 22.5 is a misprint in the manual.
or
3 - 22.5 is correct in the manual, but maybe there was a service letter recommending they be changed to 30's. (again, for whatever reason)
Sudco has them, or did two years back.
Thanks, I'll check that out... 8)
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The bikes shipped with 30's. 22.5 or 25 pilots are what is needed depending on conditions so that's what's in the PDF manual. The shipping 30 pilots and 140 mains are way too rich and you'd often find owners that just lowered the needle with the clip in the highest position trying to compensate but that creates a lean spot on acceleration -- not a healthy thing. 22.5 pilot, clip up one notch from center, #130 mains, stock discs, and ample oil are the best combo for most situations for power, economy and long life. Try it, you'll like it. 8)
Scott
http://www.bridgestonemotorcycle.com
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Scott, Thanks for jetting / needle position advise which I now fully support. Just to comfirm, do you mean fit the clip in the 2nd from top notch thus lowering the needle by one notch to weaken the mid range mixture.
As Farmerdl states above, most owners (including me) just ran their bikes with the supplied jets, assuming the BS factory had got the jetting right. It is now clear that BS initially slightly over jetted the 350 to play safe and cover all climatic and elevation conditions likely to be encountered by customers. This was a high performance 2S in it's day, the last thing BS wanted was lots of warranty claims for overheated / seized pistons.
I have found my GTO does not respond to adjustment of the tickover airscrew with 30 pilots fitted, confirming they are too big.
Bearing in mind previous comments about jet thread sizes, I took a chance and ordered 130 mains and 22.5 pilots form Motocarb here in the UK. They weren't sure if their jets would fit our earlier carbs. The good news is the 130 mains screw straight in but I've left the 140s in while running in new pistons, needle in middle notch.
The pilots tightened up after a couple of threads. A quick check showed they were standard ISO at 5mm dia X 0.8 pitch. The old jets are 0.75 pitch so I ran the new jets through a good quality 0.75 pitch die (About $7) and they now drop straight in to the old carbs. There's only a couple of thou difference per thread so recuttng doesn't take much metal off and the recut thread is not significantly weakened. The 0.75 pilot jet pitch was also confirmed in Disc Valve's old thread size post.
So if you have new pilot jets which won't fit there's the answer.
Brian.
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Brian, where did you find the 5mm x 0.75 die? I'm only finding 4mm on eBay...
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Hi Mike,
I use a company called Tracy Tools Ltd here in the UK.
http://www.tracytools.com/taps-and-dies/metric-taps-dies/5-x-75-metric (http://www.tracytools.com/taps-and-dies/metric-taps-dies/5-x-75-metric)
I ordered one carbon steel die but they actually sent me two of differing makes. The threads were distorted on one but the second die was OK and the old jet could be hand screwed in so I used that one to recut the new jets. A HSS die would be better, they are usually better quality but come dearer for something that you may never use again !!
Brian.
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Thanks Brian.... my search begins. ;D
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A quick Google search found this place: http://www.victornet.com/tools/Metric-Taps-and-Dies/327.html with the 5mm x .75 listed.
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https://www.avontapdie.co.uk/m5x075-metric-hex-die-nut-hss
Also, try this joint. A lot more pricey but it's a die nut. Would be easier to hold in the vice and screw the jet through.