TB42S Straight Petrol Won't Rev Past 3000RPM - HELP

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Originally Posted by Irish

I took from his post that he didn't have the engine running when looking into the carb and manipulating the throttle, from this:

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Yeah, I think that was the case.

I uploaded a couple of videos on below thread,showing the operation of this Nikki carby primary and secondary valve operation.

http://www.nissanpatrol.com.au/forum...l=1#post706761

RB30 & TB42 Nikki carbies are essentially the same.
They are either tuned differently or jetted slightly differently to suit each engine.
The replacement Nikki carby for sale on ebay is listed as suitable for both engines.
A good indication that it's the same carby external and internally.

There is one maybe that could be my problem as the second one was blocked

The linkages were sort of seized at first until I got some lube onto them but they seem ok now but I'll go back and make sure everything's in order but I can open the secondary using the linkage that directly operates it but pulling the throttle cable only opens it slightly

Quote:

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Originally Posted by CarbyLife

The linkages were sort of seized at first until I got some lube onto them but they seem ok now but I'll go back and make sure everything's in order but I can open the secondary using the linkage that directly operates it but pulling the throttle cable only opens it slightly

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Does it still have the LPG mixer on top of the carby or has it been removed for good?
Did you remove the fuel filter or did you replace it with a new one?

If you can get the slight opening of the secondary throttle valve by wide opening throttle when the engine's running, then it's good.
You should also see petrol spraying out of secondary venturi.

However, if you carby secondary throttle valve opens a little bit when the primary throttle is wide open(when the engine's NOT running), then
something's not right with your carby, it's been mechanically modified or it's not the original Nikki carby, but something else.

In mine it doesn't and the way the primary and secondary throttle linkages are attached, it's impossible to mechanically open the secondary
throttle by wide opening the primary throttle. They are not mechanically connected via throttle linkage, but rather connected via vacuum lines.
I guess the way it works is that the vacuum diaphragm moves from extra vacuum when the throttle is wide open & the connected arm pushed on the linkage connected to the secondary throttle valve.

Move the throttle shaft side wise and see if there's any play. If there's any play, it's possible throttle valves(both primary and secondary) get stuck. If you can manipulate the throttle shaft that way and move the throttle valves and get them to stick to the walls, then throttle body is not good, 'cos it's too worn out, which means replacing the throttle body with a used one. In that case, it's better to replace the whole carby with a used one or a brand new one.

Quote:

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Originally Posted by CarbyLife

There is one maybe that could be my problem as the second one was blocked

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Does it still have the LPG mixer on top of the carby or has it been removed for good?
Did you remove the fuel filter or did you replace it with a new one?