OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Robin Subaru Engines Thread diameter/pitch on Robin Subaru fuel tank?

Hi, I am getting a Robin Subaru EY28 fuel tank to replace an old Honda G400 tank that had rusted out. I just have to knock up a raised adapter plate so I can mount it on top of the engine, which should be easy considering these tanks mount flat.

Can anyone familiar with Robin Subaru please tell me the thread diameter and pitch on the EY28 fuel tank bolts?

I did some research and it looks as though all four are an M8 diameter, but can anyone tell me the pitch? They look like fine thread to me but I'm not sure. At a guess I would say 8mm X 1.0 but I really need to be sure so I purchase the correct thread nuts. It looks like the bolts on the EY20 and other Robin Subaru tanks are the same. The original nut is a non-serrated flange nut, part number 0023808000, but I'm sure I could just use ordinary nuts and add a washer.

Hi vint_mow,

The most common metric bolts are fine and coarse ,common fine is 1.25 mm pitch and common coarse is 1.5 mm pitch

I'd be very surprised if the bolts aren't 8mm x 1.25 mm

I usually just look at a metric thread and can tell if it's 1.25 or 1.5

I don't have a later model Robin motor here but may have an old one to check and get back here.

Cheers
Max.

Thanks Max,

I was guessing 8X1.25 as well. This photo shows the thread. It does look like a fine thread.

Yes looks 8 x 1.25mm

Thanks Max,
I'd agree with that. Once I know for sure I will post up the specs.

Hi VM,

It always pays to double check as it's difficult to see the scale of an image.

I found a EY20 motor and that was 6mm x 1 mm bolts so these are smaller than we thought.

That's assuming the EY28 is the same. I may also have a few Honda tanks to check also if interested.

Cheers
Max.

Thanks Max,

Looks like I will have to wait until tank arrives to be sure.

I compared the pic of the new tank to my old tank and it looked the same vint_mow .

The threads were all checked and I know they are 6 mm x 1mm ,I would not buy nuts online if you can go to Bunnings or
a bolt place etc as they are usually under $1. each, a pack of 16 at Bunnings is $3.90.

Your first tank image is for an EY20 motor and the EY28 tank has 4 studs that are 6mm x 1mm ,the standard 6mm bolt is usually 1 mm pitch.


Cheers
Max

The
Subaru Robin 002-38080-00
FLANGE NUT

is a M8-1.25

Interesting AVB that the EY28 tank has gone to bigger bolts.

All I really know is what I find. But I do know Subaru has closed the US warehouse per my RBI sales rep. Which is actually now a Yamaha as Subaru was sold out to Yamaha.

Thanks for the additional information. I guess I will only know whether it is the older or newer size once I receive it. As it is a new tank I'm guessing it must be the M8*1.25*17, but I won't go out shopping for nuts until I know for sure.

That one advantage of having a working shop. I usually buy things like nuts in bulk. Just be aware to there several version of these flange nuts. You want to go with the serrated version as that is considered a locking type. If you wrench or socket clearance issues you might want to go with the JIS version. It is the one I need here on Kawasaki engine's exhausts as a 13mm socket just won't fit but the JIS is 12mm socket size so it fit fine.

Fuel tank has arrived and I can now confirm that it is M8-1.25 X 30mm long.