Thumper Club Forum

Technical => Bike Problems/Questions => Topic started by: tevie54 on November 08, 2018, 09:37:45 PM

Title: Honda XL500 carb spacer
Post by: tevie54 on November 08, 2018, 09:37:45 PM
Hi, Does anyone know what the phenolic spacer that goes between the carburettor inlet rubber and the cylinder head does, do I need it? I'm fitting an XL500 engine to my XL250 so obviously there will be a certain amount of modification needed but I'm just wondering what this spacer does.
Any info would be greatly appreciated
Steve
Title: Re: Honda XL500 carb spacer
Post by: Propellor on November 08, 2018, 09:43:02 PM
A heat break I'd guess
Title: Re: Honda XL500 carb spacer
Post by: tevie54 on November 08, 2018, 09:52:11 PM
It could be although the 250 doesn't have one
Title: Re: Honda XL500 carb spacer
Post by: johnr on November 09, 2018, 12:03:33 AM
500s ran hot. they had a problem when they were really hot of fueel evaporating in the carb causing uneven running.
Title: Re: Honda XL500 carb spacer
Post by: tevie54 on November 09, 2018, 01:21:02 PM
Of course, when I googled phenolic spacer it immediately came up with heat insulator. They're no longer available from Honda and they're quite expensive second hand so I wonder if I could make one out of nylon or tufnell
Title: Re: Honda XL500 carb spacer
Post by: themoudie on November 09, 2018, 09:48:06 PM
Aye tevie,

Nylon 6.6 sheet [-40˚F to +390˚F (-40˚C to +199˚C)] has better heat resistance than either Tufnol [Continuous = 90°C, intermittent = 125°C] or Nylon 6 sheet [Continuous = 115°C, Intermittent = 170°C].

Amal supply Tufnol spacers for Monobloc and MKI and MKI½ that are 5mm thick, but I suspect are too small a diameter bore (26mm) for the inlet you have and cost £11-99 inc VAT + P&P. Amal_Tufnol_spacer_26mm (http://amalcarb.co.uk/mk-1-5-concentric/1600-series/gaskets/spacers/phenolic-spacer-26mm.html)

Alternative would be to use nylon 6.6 sheet. Direct Plastics supply (many other suppliers, I have not bought from this or other suppliers) Direct_Plastics_nylon6.6_sheet_6mm_thick (https://www.directplastics.co.uk/nylon-6-6-sheet)

Another possibility is to buy a spacer from NRP-Carbs, they also supply diaphragm kits for carbs and their products are good. NRP-Carbs_XL500_carb_spacer (http://www.nrp-carbs.co.uk/shop/index.php?route=product/search&keyword=XL500)

Hope this helps.

My regards, Bill
Title: Re: Honda XL500 carb spacer
Post by: Moto63 on November 10, 2018, 10:10:44 AM
Morning Bill, as usual your knowledge of part suppliers astounds me. I certainly know who to ask shud I ever require that elusive part..... you da maaan 👍👍👍😁🤘
Cheers, Michael
Title: Re: Honda XL500 carb spacer
Post by: johnr on November 10, 2018, 11:55:33 AM
i suppose you could buy a chunk of bakelite and get busy with the files and emery paper.
Title: Re: Honda XL500 carb spacer
Post by: tevie54 on November 10, 2018, 04:53:17 PM
Thank you all for the information, I think I shall be making one out of 1/4 nylon. I have something in the shed that looks awfully like one so I'm wondering if I've previously experimented with carb spacing on the 500RS