Author Topic: Suzuki GT 185 Mikuni carburettors on an RD 125 DX  (Read 266 times)

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Offline Alzheimer

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Suzuki GT 185 Mikuni carburettors on an RD 125 DX
« on: June 20, 2021, 06:10:46 PM »
Hi folks,

I've bought a couple of carb rebuild kits off evil Bay for the standard carbs which I intend to rebuild tomorrow, one of the chaps when I introduced myself was kind enough to let me know that the keyster kits haven't got a good reputation for quality.

With this in mind, I've bought a set of mikuni carburettors off a GT185 Suzuki because, about 40 years ago I remember a kid doing this conversion.

I'd be interested to hear from anyone who has done this conversion themselves or any advice.
I've bought some K&N filters so hopefully that'll sort the jetting but I'm not that confident and expect some fettling will be needed.
Hopefully, there's that word again, there's connections for the oil pump to the GT carbs or I'll have to fashion something to squirt the oil from the pump into the inlets...
DT50 MX x2
DT80 MX
RG 125 Gamma x2
RD 125 DX possibly!
AJS Cadwell
VW T3 auto
Obligatory auto BMW tourer.

Offline tractorman

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Re: Suzuki GT 185 Mikuni carburettors on an RD 125 DX
« Reply #1 on: June 20, 2021, 08:13:04 PM »
The Suzuki injects it's oil into the crankcase below the carbs, there is no facility to inject it into the inlet. But if the the mod has been done before, there must be a way around it. Maybe pre-mix.

Offline Alzheimer

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Re: Suzuki GT 185 Mikuni carburettors on an RD 125 DX
« Reply #2 on: June 21, 2021, 05:34:45 PM »
Thanks for the response mate. Having stripped down and thoroughly cleaned and replaced the items that the supplied kit had that actually fitted to the standard carburettors, I'll probably fit the suzy carbs. Its more for convenience, reliability and spares availability than anything else.
I'll keep the oil pump and look at either drilling and tapping an oil pipe connection into each of the GT carburettor float chambers or directly into each of the rubber intakes just aft of the carburettors.
I can't see it causing any problems tapping into the intake rubbers as the little DT50 uses a similar system.
DT50 MX x2
DT80 MX
RG 125 Gamma x2
RD 125 DX possibly!
AJS Cadwell
VW T3 auto
Obligatory auto BMW tourer.

Offline 5port

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Re: Suzuki GT 185 Mikuni carburettors on an RD 125 DX
« Reply #3 on: June 25, 2021, 07:27:41 PM »
Thanks for the response mate. Having stripped down and thoroughly cleaned and replaced the items that the supplied kit had that actually fitted to the standard carburettors, I'll probably fit the suzy carbs. Its more for convenience, reliability and spares availability than anything else.
I'll keep the oil pump and look at either drilling and tapping an oil pipe connection into each of the GT carburettor float chambers or directly into each of the rubber intakes just aft of the carburettors.
I can't see it causing any problems tapping into the intake rubbers as the little DT50 uses a similar system.

Think you will find pro carb dealers like Motocarb modify modern replacement RD type carbs with a screw-in brass oil feed spigot on a thick part of the carb, after the slide and straight into the venturi similar to OE.  They can probably supply the screw-in parts.  Oil feed into the float bowls might not be straightforward and, the extra oil with throttle does not go straight into the intake, it is diluted by the whole floatbowl of fuel.  Also, there is the small effect of the oil effecting the jetting and running slightly weaker if you feed it into the floatbowl.

5port
« Last Edit: June 26, 2021, 09:45:51 PM by 5port »
5port

Offline Alzheimer

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Re: Suzuki GT 185 Mikuni carburettors on an RD 125 DX
« Reply #4 on: June 29, 2021, 11:10:23 AM »
Thanks for the advice mate, duly noted!

As already advised, the keyster kit isn't worth buying, if anyone is in a similar position, do NOT buy Keyster kit advertised on eBay for the RD 125 DX.
NOTHING fits.
I contacted the supplier, a bike parts dealer to let them know and they simply changed the year of manufacture from 79 to 75... As long as they're making money...
Anyways, I'm currently awaiting a selection of jets and needles for the GT Mikuni carburettors and, following the advice above, I'll tap into the carburettor body aft of the slide.
I'll try and remember to get Maggot to take some pictures as we go.

Cheers,

Alzheimer
DT50 MX x2
DT80 MX
RG 125 Gamma x2
RD 125 DX possibly!
AJS Cadwell
VW T3 auto
Obligatory auto BMW tourer.

Offline tractorman

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Re: Suzuki GT 185 Mikuni carburettors on an RD 125 DX
« Reply #5 on: June 29, 2021, 12:24:57 PM »
Could be an interesting mod for RD125 owners. GT carbs are slightly bigger at 20mm compared to 18mm. Keep us updated.

Online Gr8uncleal

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Re: Suzuki GT 185 Mikuni carburettors on an RD 125 DX
« Reply #6 on: June 29, 2021, 04:20:13 PM »
Thanks for the advice mate, duly noted!

As already advised, the keyster kit isn't worth buying, if anyone is in a similar position, do NOT buy Keyster kit advertised on eBay for the RD 125 DX.
NOTHING fits.

Cheers,

Alzheimer

Yes.

The manufacturers call them "repair" kits. However, I, comic genius that I am  :o, prefer to call them "despair" kits!!  :D :D :D
Yam RD200DX (Gr8auntiepat's)
Yam FZX700 Fazer
Yam RD400C slowly getting back to standard
Yam RD350B rough
Yam RT2 almost finished
Yam DT360A almost finished
Suzi GT550J just started
Suzi 1250 Bandit regular rider
Yam RD125(A?) in the kitchen being reassembled
Yam RD250E just started
Yam DT3 just in