'72 850 Gas Tank

gene cooley

gene cooley

Autocrosser
The gas tank in my '72 850 has started to leak. Going to pull the tank Monday and have a look to see if it's repairable. If it's not repairable does anyone have new ones or good used ones? A quick check has not turned up anything.
 
I've been keeping a watch out for a tank as well. My '69 (70) had several holes after filling it with 7 1/2 gallons of apple cider vinegar & letting it soak for three weeks. I used Red Coat gas tank liner for motorcycles and a few tubes of Quicksteel, but I'd like a better fix.
 
JimD said:
I will keep an eye out for any tank that pop up for sale. Just wanted to be sure I knew what I was looking for. 🤓
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It's possible that the shop I'm working with can fix mine so that's my first choice. He mentioned gastankrenu, he had a shop in Michigan for a while, he was familiar with them.
The tanks may be different but anything we find can be compared to mine to check. Might be good info for others.
Appreciate the suggestions, I'll post some pics when we pull it Monday.
 
Jeff Stich said:
No. There are 4 different types of gas tanks for USA 850s:

1. Early Coupe/SportCoupe (1966-69) & all Sedans (1965-71)
2. Late SportCoupe/Racer (1970-71)
3. Early Spider (1966-69)
4. Late Spider (1970-73)
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Thanks for the info Jeff. That makes the search a little more difficult. At this point I am hoping that I can repair mine.
 
Jeff Stich said:
No. There are 4 different types of gas tanks for USA 850s:

1. Early Coupe/SportCoupe (1966-69) & all Sedans (1965-71)
2. Late SportCoupe/Racer (1970-71)
3. Early Spider (1966-69)
4. Late Spider (1970-73)
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Jeff what is the difference between the early and late Coupe tanks? I have a series 2 Sport Coupe which is a 1969, is the break at body change or was it due to an emissions compliance change at 1970?

Can an early tank be modified to work with a later car or late to early?

Many thanks.
 
Karl
I have very rusty 850 coupe tank and the 71 tank out of my car. They look the same except for the emissions control valves on the top, both right and left. My tank is a the shop being boiled out and they will remove the emissions stuff and close the holes left over.
 
dnudelman said:
Karl
I have very rusty 850 coupe tank and the 71 tank out of my car. They look the same except for the emissions control valves on the top, both right and left. My tank is a the shop being boiled out and they will remove the emissions stuff and close the holes left over.
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Thanks, from your description it is emissions related. My car doesn’t have a carbon canister or any other emissions hardware (as it came from the factory) beyond a interconnect from a minor valve on the intake manifold so that would apparently be the difference.

Thanks to Jeff and to you for the info. Greatly appreciated.
 
Regarding fuel tank sealants/inner coatings. These have been around for ages in the motorcycle world, mostly in small DIY kits (those tanks are small and easy to work with). But there has been a lot of bad feedback and tons of debate for the reasons why. Some believe it depends on the brand of sealant product used, others say it is the prep work, and more. I'm sure there is some truth to all of it. A few brands seem to get a lot more negative results than others, so there must be something to that. And it makes perfect sense that proper prep (which isn't easy to do - especially on a larger tank) is vital. But when they work they seem to be great. I'd at least try it first. If unsuccessful you haven't lost much, as the tank would have been scrapped anyway and the cost isn't unreasonable (particularly the DIY approach). If you want to do your own coating process then research the procedure extensively first. Either way I'd suggest adding a good fuel filter to the tank outlet after sealing it. One of the common problems is the lining product comes loose from the tank walls and then contaminates the rest of the fuel system.
 
I eventually used muratic acid to clean up my rusty tank, and broke out the mapp gas torch and some brazing rods. Make short work of the rust holes. After filling it with water a few times and getting 99.9% of them, I sealed the tank. I had never brazed before, but it was super easy and fun. Give it a whirl.
 
Got a look at my tank Monday afternoon.
There appears to be a leak around the drain plug; a possible leak at the seam and a raised rusted circle about the size of a quarter, both in the same area as the plug.
I'll get some pics this afternoon.
I also got a recommendation for a tank sealer sold by the Caswell Plating Co in NY.

www.caswellplating.com

I'm going to call them today for some additional info.
 
gene cooley said:
a tank sealer sold by the Caswell Plating Co
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That's one of the ones that has been around for a long time and seems to get decent reviews. Also the ones from Bill Hirsch, Northern, and Red-Kote are often reviewed as doing well. The ones that seem to get a lot of bad reviews are from Kreem, POR-15, Eastwood, Rust-oleum, and others. Many of them are just rebranded products from the other makers.

I have the products from several of these companies that I was asked to test as part of my consulting business, but haven't done it yet so have no first hand results to offer at this time. Funny thing is a few of them have already gone bad while still sitting in their original sealed containers (e.g. Kreem and POR-15).
 
This is the worst that I've found (so far).
20200930_150818.jpg
Still looking.
This was the raised rusted area near the plug.
 
wow. that one is bad. what about shipping it to spmone that does just tanks. it might be worth a shot.
 
Edstruz said:
wow. that one is bad. what about shipping it to spmone that does just tanks. it might be worth a shot.
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If that's the worst one on the tank we are going to repair it. Pulling the strips that protect the tank from the support straps, hope I won't find more there.
To be continued tomorrow.
 
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