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Messages - Yuppie_88 (Luke)

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CB750 / Tyre Size Advice for CB750 K4 (Avon Roadrider MKII)
« on: September 04, 2025, 09:04:29 PM »
Hi all,

I’m looking for some advice on tyre sizing for my CB750 K4. I’ve been doing some research (with a bit of help from ChatGPT), but I’d really like some human input from riders who’ve tried different setups.

My bike currently has:
Front: 4.10-19 (≈ 100/90-19)
Rear: 5.10-18 (≈ 130/90-18)

I’m planning to fit a set of Avon Roadrider MKII tyres, and I’m debating whether to stick close to stock or keep the slightly upsized look it already has. Here are the options I’m considering:

Option (A):
Front: 100/90-19
Rear: 120/90-18 (closer to stock)

Option (B):
Front: 100/90-19
Rear: 130/80-18 (chunkier look, slightly lower profile)

Option (C):
Something else entirely — if you’ve run different sizes that you feel work better, I’d love to hear.

2
CB750 / Re: First Start Attempt – K4 Project (Advice Welcome!)
« on: September 01, 2025, 07:59:44 PM »
Just a quick update, thank you again for everyone's advice.

It runs and rides, I took a slow ride out on Sunday to Cannon Hall Farm near Barnsley for an ice cream! Here's a link to quick video of the first start https://youtube.com/shorts/h7t6eVguyjg?si=Y6qPpfkztvx-6jsJ

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CB750 / Re: First Start Attempt – K4 Project (Advice Welcome!)
« on: July 31, 2025, 09:08:43 AM »
Thanks everyone, I wouldn't have thought of this - super helpful.

The fresh oil was added around 10 months ago, I've noted that the oil tank level has dropped considerably (no visible oil leaks). I'm assuming this is because the oil has now worked it's way into the sump. Would it be preferable to drain the sump and add back into the oil tank or leave it as is?

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CB750 / First Start Attempt – K4 Project (Advice Welcome!)
« on: July 29, 2025, 09:49:01 PM »
Hi everyone,

I’m getting close to attempting the first proper start on my K4. I bought it as a non-runner from DK Motorcycles - it did fire briefly on Easy Start at the time. I’m a novice, but really enjoying the learning process and taking my time with it.

Before I hit the starter, I’d really appreciate any advice or tips from those with more experience. Here’s what I’ve done so far:

• Loom and electrics overhauled
• New battery
• New plugs (checked the spark across all four cylinders)
• Carbs fully rebuilt
• Cam chain tensioner adjusted
• Fresh oil in (I’ve held off on the filter for now - planning to get it warm, then dump the oil and do a full service)

My main concern at this point is making sure the oil is circulating properly on first start and how to check - though I’m sure there are other things I might be missing too.

Any input or suggestions before I go for it would be hugely appreciated. Thanks in advance!

5
CB750 / Re: Carb Gasket Sets; Pattern vs Genuine
« on: June 30, 2025, 07:01:31 PM »
Thank you, I bit the bullet and went for the genuine set. £100 worth of rubber!  :'(

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CB750 / Carb Gasket Sets; Pattern vs Genuine
« on: June 28, 2025, 09:29:55 AM »
Hi all,

I'm in the process of stripping the carbs on my K4. Does anyone have experience with the David Silver pattern parts carb set? Are they any good? Or should I consider spending the extra £60 difference for the genuine sets.

Thank you

7
CB750 / Front-end rebuild - Clutch safety switch
« on: June 04, 2025, 08:59:09 PM »
Hi everyone,
It's been a while since I posted here; I'm finally making some progress with my front-end rebuild on my K4.

Right now, I'm connecting up the wiring harness I've refurbished, but forgot about the clutch safety switch (I have a new one to install). Should this be routed inside the handlebars with the rest of the switchgear or, externally?

8
CB750 / Re: Wiring harness connection to battery tray (with pics)
« on: August 15, 2024, 11:55:47 AM »
Yep, on mine (750 K4) there is no side stand switch either.

The safety unit is unfortunately discontinued - I spoke to David Silver today to confirm. This means I'll be jumping the safety unit connection as BigAl mentioned.

I've found a nice electrical box online which has 60mm centre mounts, this should bolt on directly to the original safety unit mount (could be a nice place to keep some spare fuses too). I intend to run the jumper connection through the box to keep things tidy and add a nice new connector block on the end of it. I know I'm the only one who will probably see this but, I don't like the idea of this thing flapping around ;D 

9
CB750 / Re: Wiring harness connection to battery tray (with pics)
« on: August 12, 2024, 08:56:48 PM »
Quote from: McCabe-Thiele (Ted) on August 12, 2024, 08:33:42 PM
Kojaycat do the block connectors.

Brilliant, I'm assuming it's the 3.9mm Japanese bullets?

https://kojaycat.co.uk/epages/950000457.sf/en_GB/?ObjectPath=/Shops/950000457/Categories/Connectors_Bullet/39mm_Japanese_Bullet_Connectors

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CB750 / Re: Wiring harness connection to battery tray (with pics)
« on: August 12, 2024, 07:54:26 PM »
Thanks everyone for the replies, it sounds like the first point of call is to check good ground connections to the frame then.

I noted from the wiring diagram; the regulator, rectifier and safety unit all ground via the ground wire bolted to the frame where the seat lock latch is, whereas the starter and starter switch obviously get ground from the engine. 

A few parts arrived today so that should keep me busy this weekend. The connector blocks and bullet connectors look a bit crusty in places, does anyone recommend anywhere best to get replacements to keep everything nice and standard? 

11
CB750 / Re: Wiring harness connection to battery tray (with pics)
« on: August 11, 2024, 09:59:57 AM »
Pics

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CB750 / Wiring harness connection to battery tray (with pics)
« on: August 11, 2024, 09:58:30 AM »
Hello everyone, I'm new here  :)

I've recently purchased my first CB750 K4, a US import from a dealer. I've done some basic restos in the past, mainly on smaller engines (DT50, CB125, YZ125) but I would consider myself a newbie wanting to learn really.

Anyway, the bike was running at the dealership after being hot-wired and setup on a dummy fuel line. Having got it home I started to investigate the wiring a little further and found that the fuse box and the safety unit were missing, the live battery cable was also corroded (see pics). Replacement parts are on their way.

My only concern is, it looks as though there has been some heat in the wiring at some point - the harness tape looks like it's melted in some places. I can't see any bare copper wires showing, the wire insulation looks ok. That being said I'm still a little concerned about hooking up a battery to it - fire extinguisher at the ready!

A couple of hypnosis I've pondered (this is where I would appreciate your expert input)...

1. Maybe someone at some point, has hooked the battery up the wrong way round, hence the melted tape and the looks of the starter ground wire.
2. There has been some external heat in this area (unrelated to the wiring), hence there isn't any bare copper wire showing (seems unlikely to me though).
3. There is a dodgy ground somewhere in the harness. There is evidence that someone might have been playing about with the indicator electrics and headlight.   

Any thoughts or observations are appreciated

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