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Discussion Starter #1
Greetings to all those GS450 Cafe Racer Riders. I know you are out there cause I see hundreds of these bikes on Google images. I have a question, how did you get your bike to run good in the mid range with the Pod Filters installed. I acquired a 1981 GS 450 with an aftermarket exhaust with 2 into 1 pipe, with baffles and Pod filters installed. The carbs are Mikuni BS 34 with 120 main jets and it's better than it was with stock jets but still a huge lag in acceleration. What set up does anyone recommend to get it back to smooth as stock performance?

One more question, Has anyone pitched the BS 34 carbs in the dump and replaced them with something else? I am finding parts for these carbs very hard to find and Very Expensive...

Thanks for any input. I know I'm not alone.
 

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Hi, you will never get the CV carbs to run right without the stock airbox. Like never, ever. Or any other guy with a GS 450. You should realize that guys on GS 450 chat on the internet are probably basically lying when they say their bikes run well with pods. The phrase 'Tuning to a standstill' , comes to mind.

Put the stock air box back on.

Forget buying aftermarket carbs, I doubt they will work anywhere near as good as stock, without a proper dyno tuning from a professional Dynojet dyno motorcycle tuner. Motorcycle parts can easily cost ten times the price of the same kind of car part, get used to it, sonny.

Read this about ten times: http://www.caferacer.net/forum/tips-tricks/19639-pod-filter-thread-geeto.html

You are not alone. Half the cafe racer world has bikes that run like crap with pod airfilters on CV carbs. It's a monkey - see , monkey - do , lemming type event.

Danger, is my business."
 

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Discussion Starter #3
You are the second one to tell me that today. I don't have the original air box so I'm stuck with pods until I find a box. Maybe I could figure out what effect the air box has on the carbs and find a way to replicate that through a different looking air box. Any thoughts on what the air box does to the carbs? My guess is the original air box causes air intake restriction which could possibly be duplicated by blocking air or a "restricter" plate on the intake side of carb. The other thought I had is since the air box connects both carbs together, maybe one sucking air in while the other is not has some effect on airflow through the carb, hard to describe what I'm thinking.... I really like the cafe racer look which doesn't include a factory air box, I'd be open to making something that looks unique but recreates the environment of an air box for the carbs.
 

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Take some sepia photos of the bike as an art work at an old warehouse with paint pealing off. Art works.

Then go find a stock airbox and fit the sucker. Now bike works.

This might be an appy old world where you can find drivers for some old game that only runs on MS Millennium Edition, but that's software, not carburetor engineering and tuning.

You have to realize some 'open triangle' pod plodder cafe custom motorcycle is an art work, not a 'bike's a she a work.'

Some of the world's best tuners probably couldn't tune your current setup, so don't waste your brain space and meagre cash persisting with a task you can't successfully accomplish.

Danger, is my business."
 

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I run BS40 (same family of carbs but some differences internally) on a two stroke with pods and with stacks and open and it runs fine thank you very much. Unlike Keihin CV crabs on Honda twins the BS series are not so hard to tune.

First place to start is with the pods. Are they cheap EMGPO crap that partially block the air inlet? If so, you know what to do next. If tehy are decent pods and by that I mean K&N, UNI, RamAir, Pipercross etc, then work out what revs and throttle position it's bad and when it's good.
 

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Discussion Starter #7
Honestly I don't know what brand of pods they are. They are cheap pods for sure. I will have to look into this closer. Thanks for all the advise, I will keep you posted. I am waiting for some carb gaskets & Orings which my suzuki dealer says are on back order, however another small local small bike shop laughed and said they'll be on back order forever so I'm not to sure I will even get them.... That's why I wonder if I should just be looking for a different carb.

I get what your saying Witworth, basically, if it works don't fix it right.... Well I'm a mechanic by trade, not a motorcycle mechanic but I do work with gas engines everyday & I may not be able to tell anyone in a scientific way, how the airflow & fuel atomization gets done when passing through a BS 34 carb body but I do believe that no matter what the only thing that matters is that when the fuel & air show up at the intake valves door step it needs to be the right ratio and atomized, I doubt that the only carb able to do the job is a BS 34. I have a Honda shadow for when I want to ride a 400 mile day, the Cafe is just my tinker toy and who knows maybe I can make my own air box out of my Grandfathers old steel lunch box and it'll work perfect. Sometime the fun part about building a bike is understanding what needs to happen and then getting it done "thinking outside the box" no pun intended. atleast that's the fun part for me. I hear what your saying Withworth and if it were my Honda shadow I would agree 110%, but for the Cafe, I'm going to rebel and leave that air box on the swap meet table and find something cool that'll work. :cool:

I'll keep you posted.
 

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Get some K&N's and not the smallest ones you can find. You need filters with enough flow to allow the motor to run right.

Making a DIY airbox is a good waste of time. Not a good way to get the bike running right.

You will spend weeks tuning it. Or months. Or years.

Danger, is my business."
 

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The GSResources is a huge source of info on everything GS.

This page is a greeting page and has links to carb rebuild tutorials, Valve shim procedures and a "shim exchange club"...all kinds of info. There is even a link to a guy who sells the o-rings you need. his kits basically give you every o-ring you need for a carb, and in good quality rubber that withstands gasoline.
GSR Greeting
 

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Don't forget MikesXS he sells all sorts of parts for BS series carbs. Some of them will fit your carbs - like the shaft seals and gaskets and so on.
 

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I hear what your saying Withworth and if it were my Honda shadow I would agree 110%, but for the Cafe, I'm going to rebel and leave that air box on the swap meet table and find something cool that'll work. :cool:
Well if that's the attitude then K&N filters and maybe one or two up on the pilot is also in order. The GSRecources is an excellent recommendation from 8ball.
 

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Discussion Starter #13
I tried GSresources but you must need an actual computer. My iPad doesn't seem to open certain selections. Just wondering what carbs does the 1st gen GS500 have?

image.jpg
 

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450 carbs on the left, 500 carbs on the right:



The 500 carbs are half the weight of the 450 carbs (about 3lbs v 6lbs)
 

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Discussion Starter #16
I just went to the GSresource site but now I just hit your GSR greeting word and see what you are sending me. Thanks 8ball it looks interesting.

So does the gs500 carb assembly fit right on the 450 engine or is there some differences with the mounting? I looked on eBay and seen two different sets for sale for the same price as the cost for one diaphragm for my carb. Plus there are tons of parts for those carbs. I'm very interested In this idea. I'd love to know more details if you have any..
 

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I think the GS500 carbs would be an easy swap with little hassle.

But to be sure, check out a GS twin specific forum. They probably even have jetting suggestions for K&N individual filters.

Danger, is my business."
 

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The 1st gen (88-92) GS500 carbs are the sought after ones because they have air box rubbers off the back of the carbs (the later ones had the air box screwed onto the back of the carbs). You can mount pods onto these ones.

From what I have read they are pretty much a straight swap with no re-jetting required. there is a GS Twins forum but it is mostly biased to the GS500, so GS Resources is your best bet for detailed info.
 

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Discussion Starter #19
Would "California" carbs be basically the same as non California carbs? I can get my hands on a set of gs500 carbs from a 92 gs500 but they are California carbs. Any thoughts...
 

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Not 100% but I don't think the carbs themselves would be any different. I think the CA differences meant the carb vents went to a charcoal canister instead of straight into the atmosphere, and a few other differences (not carb related).

Again, GS Resources is probably the best place to ask.
 
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