79 Special II RestoCustom "Doomy"

Our oldschool method of determining jet size and orifice diameters was to take the orifice diameter, in millimeters, and multiply by 100.
:umm: eeks. Well I have one other set of #135 main jets and 27.5 pilot jets. I'm pretty sure they pin check size the same but I'll look tomorrow. If I've over jetted that much , I'll just saw off the mufflers and run straight pipes :lmao:
I could not find a reliable jet hole size chart... It is really cool how easy it is to drop the float bowls and change jets on BS38's :thumbsup:
 
looks like it has great potential. A chance to stretch your creative muscles! I’m looking forward to seeing what you do with this. :)
Thanks Bob ! Yes, I am going to let some creativity flow. This 79 is catching my interest more and more. My best shocks and double disc brake parts and such are migrating on their own towards the 79 Cafe in the nights. Looking forward to all that happens myself even..
-R
 
...I could not find a reliable jet hole size chart...

Well, maybe a rethink here.
Most of my experience was with Honda Keihin jets, which conform to that sizing scheme. Here's a chart compiled by another member, showing the Mikuni jet numbers being smaller...

JetSizes.jpg
 
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Virgin 78/79 Mikuni original jets Have to clock in for awhile,
Thanks everybody o_O
-RT
 

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Stashing these carefully selected carb items here for this 79 BS38 set. Score :D
Still on track but the set must go home for cleaning/assembly
-R
Check out the as found bowl condition I pulled the jets, mixture screws, etc out of..
-R
 

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Ironically I manufacture to fit very very tight tolerance (.0001's) bores everyday lol :lmao:
 

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Mikuni #135 on that chart shows .061 ?
Not what I find.
Me neither. Here's a new Mikuni #135. I don't have your fancy standards Randy, all I got is a set of tip cleaners. A .048" is a loose fit and a .055" won't fit. I've checked that caliper against my mic. standards and it's within a thou. across it's range.

IMG_20191127_111010.jpg
 
Looks like a "reliable jet hole size chart" needs to be acquired, or built.

One of 5twins' pics of the later VM22/210 76-79 pilot jets shows that the metering orifice is at the top of the jet, rather than the bottom of the other BS30/96 pilot jets.

XS650CarbSpecs02.jpg
 
Perfect sense on #54 (.055)
The main jets are big and meaty to uphold original size.
The Pilots shape inside and size tolerance is much more critical ?
Assuming ..
 

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For me, much of this jet sizing was a bit of a black mystery. For example, in the early '70s, we encountered VM series mainjets that were marked double their expected size, like #280 mains that had the same orifice as normal #140 jets. Figured that it was maybe a way to ensure that VM jets stayed with VM bodies...
 
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