Carb question!

TBM

TBM

Club Member
Got my 1984 FLHT home, and now starting on the big fix up and the first of MANY questions no doubt!

It appears to have a Mikuni HSR 42 Carb. However the throttle pump isn't working, the plastic throttle pump lever is broken (i think?) and it has no choke cable fitted.

I am completely new to Harleys - Is it worth getting it all fixed (carb rebuild kit, new choke cable, new throttle lever) or is there an alternative/better option? I am on a bit of a budget.

Secondly - the air filter bracketry is a bit shonky. Is there an alternative filter/bracket I could use if I keep the MSR?

Thank you - Phil

IMG_20240410_085203.jpg
 
40mm Mikuni is a good carb, I ran one on a FXR and it was very good. Personally i would get the spares and rebuild. I would hope they do a full rebuild kit that includes the part your missing
 
I think I'll go for a rebuild. Just need to ascertain if it's the HS40 or HSR42 - any one help? Looking at numerous photos, the set up on the top right of the carb (when looking at it) is more like the HS40. Any markings on the carb I can look for?
 
It’s a 42mm hsr The Phillips head screw controls the pump start point there is a threaded flat head screw to set the stopping point on the top of the carb just visible in pic it looks like a gorilla has wound the pump screw in back it out and the pressure arm should come down onto the rod leave about 1mm clearance between rod and plastic you can see the telltale where the top of the pump rod has been touching the plastic the brass screw on left is mixture set to 1-3/4 turns out from lightly seated it will give you a baseline setting to the left of the mixture screw is the idle/tick over adjuster on its wobbly line use it once started to get an even idle Allen’s performance do an overhaul kit for them i have got an exploded parts diagram i will try and upload it for you
 
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That's great thank you. I think I have an issue with parts 77 and 78 as the accelerator pump is sat right at the bottom and is not spring back up. Should be an easy fix with the right parts. I'll order a kit.
 
The rod seizes where it passes through the carb body half way up free it off first then emery paper it that should suffice then undo base of carb and check diaphragm it usually gunges up there 77 aand 78 are the spring and rubber boot generally prob free
 
It's loose - I can move it up and down easily by hand, but theres no fuel squirting going on so thinking it may also have got detached from the plunger?
 
Sorry my bad 77 is the plunger assy they sometimes stick down the bore in the float bowel when old fuel evaporates and the residue makes them stick down need to pop bowel off to be sure
 
On the Manifold Side of the Carb. Body there will be a number stamped, if it is a Genuine Mikuni. It may me "TM42" or HSR 42. Both the same Carb. If there is no number you can measure the Manifold side of the Throat and it should be 42mm for 42 Carb. or 40mm for a 40 Carb. (y)
 
Stripped the carb down and the pump plunger was well and truly jammed down the bottom of the float bowl. Had to drill a hole in it and use an extractor to get it out. No spring underneath either! Have ordered both so can get her rebuilt asap.

Seems I was also missing an adapter plate for the front of the carb, so have bought one of them, a new filter and filter bracket (that I can also fit my choke cable to - the choke plunger was present, but no cable).
 
Here mate look at this its important if its not right you will have tuning and set up problems….
IMG_5892.jpeg
 
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Yes, from that it I looks like I have the Harley nut and Mikuni spring and plunger. Thankfully!
 
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