1989 and 2004 carbs

[mab32]

Hi again,
Are the 89 carbs BSR34 type, if so what are the 2004 carbs.
I want to put the 04 carbs on a 89 engine but want to rebuild/clean the carbs first and need to get the proper "O" rings etc.
Thanks again

[mister]

2004 carbs are 3 circuit. 1989 carbs are 2 circuit. If you try to put 04 carbs onto an 89 you'll have issues. It's not a straight swap. Not plug and play.

Michael

[mab32]

Thanks for the input Mister !
What issues am I looking at ?
Are there extra vacum issues or is it the mid range main ?
I assume it can be overcome, I hope....

[gsJack]

The 2 circuit carbs were BST33 models as indicated in my old 97 Owners Manual and the 01 and later carbs are the BSR34 models as indicated in the 06 specs in the wiki.  Biggest difference as far as mounting is the 1 mm larger throttle body, the manifolds changed with the 01 and later models and I think you would need some of the newer ones for a proper fit.  They all mount to the cyl head with the same flange bolts so they can be exchanged.  Another thing to consider is the change from 1 throttle cable to 2 cables starting with the 01 3 circuit carbs, no doubt you can work around that.  The throttle position indicator on 04 and later carbs would be discarded.

I've long said the change from the 2 circuit carbs to the 3 circuit carbs was the biggest performance change made to the GS500s as far as everyday riding goes.  The bike pulls stronger and smoother thru the mid range and all around in general except at the top end and also pulls from a lower rpm at the bottom end, needed 4k rpm to get the 97 pulling smoothly and my 02 pulled nicely from 3k rpm.

I rode both my old 97 that I had put 80k miles on and my almost new 02 with only about 4k on it back then for awhile and the difference was obvious to me.  Yet that 97 with 80k miles on it still pulled a bit stronger on the top end.  I have 92k miles on the 02 now and never touched the carbs on either but my bikes never sit and dry out for long.  Could be there was a cam change too between the 2 and 3 circuit carb models but I've never been able to confirm that one way ot the other.

[mab32]

Thankyou gsJack, that's what I was looking for.
Great information !

[The Buddha]

04 carbs fit an earlier mainfold. The ID is larger on the newer ones but the wall is thinner and they do fit. The problem AFAIK is the dual throttle cables and the plethora of hoses and wires and BS in the new carbs. Get em all capped and sorted and its a fit.
Cool.
Buddha.

[Cosimo_Zaretti]

Finally getting to finishing my own engine swap, and I have an 08 motor complete with carbs which I have bolted into my 1995 frame.  It was suggested to me that I discard the 2008 diaphragm cap and and use the caps of the 1995 carbs, to simplify the need for additional vacuum hoses.  Would I need to replace any seals if I swap these over?  Could I just blank off the holes on the existing caps?

[The Buddha]

I doubt the caps off the 89-00 will fit an 01+, 01 and 02 caps would fit the 04 I think.
Cool.
Buddha.

[Cosimo_Zaretti]

For the time being I think I'll grab the boots off my old motor to bolt up the '95 carbs, which will keep the plumbing the same with the airbox, tank and petcock.  The dealbreaker was the twin throttle cables.  Hopefully the new motor flows similarly enough that I won't run into immediate jetting issues.  As far as I know it's basically the same head, valves and cam, so with the original exhaust and airbox, I should hopefully be able to run the same carbs.

Sorry for the thread hijack.

[mab32]

I want to thank all you guys for the good info !!
Cosimo_Zaretti don't worry about hijacking the thread, sometimes you read something and just have to ask your own questions, it's all good.