4H7 Fuel Tank Restoration

So after refinishing the tank and side covers on my 1982 XJ650J I decided that it would be a good idea *cough* to buy an XJ650 tank that was in kind of rough shape and see if I could restore it.

Getting started on my original Xj650 refinish project:
https://www.xjbikes.com/forums/threads/underside-of-fuel-tank.129719/

Finishing the original Xj650 refinish project:
https://www.xjbikes.com/forums/threads/1985-xj650-maxim-refinish-complete.129841/

So then I did what any rational person would do and bought a questionable part off of eBay.

I bought what was advertised as a tank off of a 1981 XJ650.

A little bit of research seems to indicate that the 4H7 tank was used on 80, 81, 82, and 82 XJ650.

Here is what I bought:


Some nasty dents, but not a basket case. Not too rusty inside. I should be able to treat the rust and use the glue pulling technique to pull the dents out enough make it re-finish-able.

There are people that do glue pulling that can restore a panel to perfection. I'm not one of them. First, when you glue pull on one of these old tanks, the crappy old paint and clear coat tends to rip off. Second, I'm just not that good. The pros are great at getting door dents out of your Audi, but I don't need to be that precise because I'm refinishing anyway. My goal is to end up with less that 1/16" filler depth.

After a few nights of glue pulling, it is looking a lot better:


Next steps are to do a rust treatment on the inside. Not sure when since riding season is coming - if it ever warms up in Minnesota.

After that, a little bit of body filler. They say maximum depth of body filler should be 1/8". I shoot for a lot less than that. All of the glue pulling should result in filler depths of less than 1/16".

 

you could use lead to fill it

 

True that. That might be worth a try just for fun. I suspect I would still end up doing a glaze coat of filler.

It's really just a game of removing imperfections step by step, so I could certainly insert a lead step in there to reduce the amount of filler needed.

I've also seen cases where somebody just went ahead and filled a dent completely with filler without trying to straighten the substrate at all. Not recommended. Much quicker, but not recommended. Much more profitable if doing the repair for profit, but not recommended.

Back in the day repairing body panels we also used to drill holes in order to attach a slide hammer. Luckily I don't think that is done much anymore since we have stud welders and glue pulling techniques that we can use to straighten the substrate without drilling holes. Which I think is pretty important for a fuel tank - you don't really want holes in your fuel tank.

 

Just use reinforced fiberglass filler for the deeper repairs.

 

Personally, I would only use fiberglass to repair fiberglass.

 

Dan the dent puller you use is it the harbor freight one? Where did you get it I would like to buy one that someone has had success with.
I have a dent to fix , the dent is a little sentemental reminder for me but it is time to fix it.
I see HF has a welder for the nail type for 99$ may give that a try. just nervous about welding to a fuel tank.
maybe use a tire inflator and fill the tank with co2, maybe just over thinking my safety

 

my dent is a little larger than yours and where the emblem is on the tank.

I am the only member of the MKMC .
a few others have tried to join but were not sucessful in the qualifcations needed.

 

PREFACE: Bodywork, removing dents, painting, etc., seems like an easy task - but as with most things, it is usually not as easy it seems. I assume no liability for outcomes related to listening to my advice.

I mostly use the glue pulling technique. Basically using a hot glue gun to attach tabs to the surface and then using a tool of some sort to "pull" on the tab to move the substrate.

Glue pulling requires a ton of patience and the willingness to examine the surface for highs/lows and decide where to put the next tab. It is not for everyone. I, myself, am not a very patient person by nature, and I use glue pulling as a way to help myself become a more patient person, if that makes any sense.

Most people don't have the time and/or patience to deal with a glue pull - they want it done and they want it done NOW. Which leaves you with two options: First, the cheap option of drilling a hole and using a slide hammer - really bad idea for a fuel tank. Second option is a stud welder with a slide hammer - even cheap stud welders are not cheap and would probably not be a good option for fixing one or two dents.

On XJ sheet metal, glue pulling will most likely rip off the original coating. The bad news is that you have ripped off the original coating, but the good news is that you probably want to refinish it anyway. If it was not the original coating (i.e. it has been refinished already) then who cares. The original coating on a 1980-something Yamaha is total crap compared to modern day OEM coatings or anything we would apply now.

Here is an example of a starter glue puller kit:
https://smile.amazon.com/Super-PDR-...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

@XJ550H - If you have a dent around where the emblem is on the tank, then you may need a lot more pulling power than glue pulling. The angles and bends that create structural rigidity to metal substrates also act against you in this scenario. I would think a stud welder would be a good option to straighten out the substrate - can do a lot of pulling without compromising the integrity of the substrate.

Here is an example of a "starter" stud welder kit:
https://smile.amazon.com/Bestauto-U...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

The Harbor Freight item should be pretty similar, I think.

As you can see, the stud welder is more expensive to start than glue. But also note that stud welder requires a way to remove the studs - in other words, you need a grinder.

In conclusion, after way too many words, the best option really depends on what you are trying for. Your results may vary.

 

Dan, you could also get a 750 Maxim tank.....it is a drop on/bolt on replacement. Absolutely no modifications, and it give y0u an extra gallon or so of fuel capacity.
Dfox

 

I have a grinder and this would be the first time it was used on a motorcycle

paint not an issue.

my other option is dent in the other side to match and hammering tin to shape is not something I am good at


those are nice kits look like they have every thing you need to do the job.