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Ren - The Ed¹ said :-
So... What exactly is the engine from. Suzuki DRZ400, what year and any other model details? Is the carb likely to be original to the engine. In an ideal world there'll be part numbers on the carb and/or TPC.
I'm sure there'll be a parts diagram online, it's a case of finding the right one. That'll help us work out if there's a widget connecting the 2.
03/03/2026 07:38:37 UTC
Ren - The Ed¹ said :-
Does this look at all familiar?
03/03/2026 08:01:59 UTC
Ren - The Ed¹ said :-
Ah - the above carburettor seems to be a Mikuni, most of the DRZ400 carbs I'm coming across are Mikuni but you have informed us yours is a Keihin. I'm wondering if you have a trick carb fitted with the TPS for the Mikuni just screwed on to stop it flopping around.
03/03/2026 08:10:21 UTC
Ren - The Ed¹ said :-
The most common Keihin for the DRZ seems to be the FCR. There's an exploded diagram on the link below and if you find item 109 there seems to be a widget between the throttle shaft and the TPS...
https://www.frankmxparts.com/Keihin-FCR-MX-37-39-40-41-flatslide-carburetor-part...
03/03/2026 08:19:29 UTC
Glyn said :-
I thought it looks to me that those 2 parts fit together but then realised that Ed posted the picture not Ian. On the Keihin carbs fitted to the ZZR they did not alter the mixture in any way that I could see but, obviously, altered the CDI to alter the timing. My Yam Diversion had a faulty TPS and ran like a barrel of bolts until I replaced it.
03/03/2026 08:48:39 UTC
Ian Soady¹ said :-
Thanks all, it is an FCR as referenced by Ed in his link - and ironically it's where I've ordered the choke assembly from! My engine being from a CCM it's the high power version(!) It is indeed part 109 I'm missing. I forgot to add pics but they will be shown below. I'm told by someone on a dedicated forum that I don't need it as all it does is change the advance slightly when idling and in gear to prevent stalling. Glyn you're right there's no way the mixture can be affected as there's no connection to the carb from the ECU apart from the TPS.
I don't believe I lost that part as I took it apart carefully and have searched the bench top. A previous owner had done some extensive work on the carb, documented by various changes to jets etc and I think he must have lost it.
My current plan is to leave it off and make a cap from nylon to fit over the spindle end to avoid air leakage. I assume - maybe wrongly - that if the ECU doesn't see any resistances then it will revert to some default setting, however Glyn's experience with the Divi makes me wonder.....
This is the carb end:
03/03/2026 10:17:33 UTC
Ian Soady¹ said :-
and this the sensor. It wouldn't be impossible to make a link piece if necessary.
03/03/2026 10:19:02 UTC
Upt'North ¹ said :-
My experience with electrotrickery is if you depart from standard it'll probably upset some'at else. Plus I wouldn't want to run a fairly stressed engine with incorrect ignition timing. Pistons shouldn't have holes in them, ask me how I know?
Upt.
03/03/2026 11:00:48 UTC
Ren - The Ed¹ said :-
Firstly - the TPS Ian is holding has 2 holes... the carb Ian pictures has but one threaded hole to secure the TPS. Looking on the exploded diagram in my link it actually looks as though that is by intentional design! Cheapskates pffffft.
Secondly it looks to my eye that you'll be looking for - essentially - a flat piece of plastic! There's a slot in both the carb side and the TPS side, perhaps a bit of random plastic can be filed down to fit? There is the risk the correct item may have an offset in which case... urgh.
03/03/2026 11:51:14 UTC
Ian Soady¹ said :-
Thanks both. Well spotted Ren - I omitted the flat plate for clarity. This has 2 threaded holes for the 2 slotted holes in the sensor and one for the securing screw. This is spaced out with 3 washers and an oversize nut which strikes me as non-Suzuki..... Interetingly the exploded diagram doesn't show the plate.
I'm buying the cable operated choke from a place in the Netherlands and having found the part number see they actually have the connecting bit of plastic in stock. It's only a fiver but postage adds another 6 quid or so. Can't decide whether it's worth it. It does look as though the 2 blades are indeed offset.
03/03/2026 12:16:51 UTC
Upt'North ¹ said :-
Small price to pay for piece of mind Ian. Good shout on the offset.
Postage is a killer ain't it. Every package I post these days is over a fiver. Just posted a birthday present off to Staffordshire, because it was over 1 kg and a medium size, "that'll be £6.80 sir". Just posted a letter to the USA at the same time, I think that was £3.40 for two pieces of A4.
Pffffffftttttt.
Although it's cheaper and more fun than driving to Smoke on Stench. On that note our fuel in the village goes up at 1 pm due to you know what. Damn decent of them to tell us beforehand.
Upt.
03/03/2026 12:50:31 UTC
nab301 said :-
My only experience with a dodgy TPS was on a fuel injected Guzzi , the throttle was a little snatchy and checking the resistance "curve " of the TPS with an ohmmeter proved it wasn't very progressive , as an experiment I started the bike with the TPS disconnected and like Glyn the engine barely ran except on full throttle . The original problem was cured with a new TPS although unlike a carbed engine there must be more at play than just ign timing?
Nigel
05/03/2026 15:06:15 UTC
Ian Soady¹ said :-
My parts are now in Frankfurt apparently but one their way to me. When I look at the carb there doesn't seem any way the cable operated chioke can fit along with the TPS as there's only clearance (just) for the shaft of the carb-mounted choke button. I think I'll have to chop one leg of both the bracket and sensor off to get it to fit. But will wait till I get the bits. Always something isn't there? The carb is humongous and incredibly complicated but apparently releases another few bhp over the CV Mikuni which is standard fit on the softer models.
I've just heard that the sidecar body & mudguard are finished so have arranged for them to be picked up tomorrow morning. How exciting!
06/03/2026 11:05:53 UTC
Glyn said :-
I can’t wait for the pictures Ian. I’ve been busy myself on the Trumper Triple. The main issue being the “stuck” clutch that would not release. It was an easy job to get it out and find the metal and friction plates glued together with gloopy old oil. Just a quick clean up of the metal plates with metal polish and all is well. I had to make a new cover gasket as £30 for a genuine item seemed a bit steep.
06/03/2026 18:40:49 UTC
Glyn said :-
All back together on the engine now and stainless fasteners making it look much better. I’ve bought a new battery and just have to do the Kreem tank sealer job to keep the rust at bay. The MOT is booked for 2nd April.
06/03/2026 18:44:39 UTC
Ian Soady¹ said :-
Ah, the almost lost art of gasket making. Did you use a cornflake packet or the proper stuff? I have sheets of the latter - can't remember the name - which are decades old. I must admit to often using RTV except where bits might get into the oiling system these days. Primary drive covers on my old bikes are notoriously difficult to seal otherwise.
07/03/2026 09:38:22 UTC
Ian Soady¹ said :-
Quick pic of the painted body and mudguard. The paint shop (Lee at Painttech in Bromsgrove - see link) has done a really nice job and the colour match to the bike is just about perfect. I'm leaving it for a week or so to fully harden before applying the chrome strips, tonneau clips etc.
Cost £675 which sounds a lot but given the work involved I think was very reasonable, as was the £40 each way transport by a local man & van. Shiply and anyvan wanted over £150 to take it about 10 miles which is about what I paid to have the whole lot brought from Wisbech to Redditch. And that by a proper bike removal bloke (Phil from Acceleration) who really knows his stuff.
https://painttechrepairs.co.uk/...
07/03/2026 12:16:35 UTC
Ren - The Ed¹ said :-
Well for a fella with a dicky knee you're doing some excellent work there Glyn. Colour me impressed.
By golly that's very very red Ian. I have little sense of colour but I'm thinking the chrome trims and black frame will reel it in nicely.
07/03/2026 17:44:30 UTC
Upt'North ¹ said :-
Nice work fellas, I've cancelled the callback from MI5....at first I thought it was a Shahed.
07/03/2026 17:50:58 UTC
Glyn said :-
Looking very good Ian. I’m always worried about new paint and I struggle to let it harden wanting to get it together as soon as possible. It takes a fair bit of willpower to leave it. I bought the proper gasket material some years ago and still have lots left.
07/03/2026 20:10:04 UTC
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