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Author Topic: 1981 Suzuki GS450L - Cruiser to Scrambler  (Read 38248 times)

Offline advCo

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #80 on: Aug 29, 2016, 15:00:28 »
I'm pretty sure most of the rattle can engine enamels do not achieve chemical resistant until they are cured properly, unless rustoleum is different i'd be cautious with the fuel  :o

Offline jpmobius

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #81 on: Aug 29, 2016, 15:13:52 »
Right.  I've never seen a single component paint that was "fuel resistant" - unless fuel resistant is like a watch that is "water resistant" for up to one inch of water!  The paint may not "rinse off" when you spill gas on it, but I'd bet gasoline will leave a mark even if you have a rag at the ready.  Baking it very likely will help, but it won't be like 2k urethane or epoxy which are more like "fuel proof".  You could scuff it and shoot some more durable clear over it quite easily.  The 2k urethane spray can clear is expensive but worth it.  You've done a lovely tasteful job - worth preserving!
Mobius


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Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #82 on: Aug 29, 2016, 15:14:43 »
I'm pretty sure most of the rattle can engine enamels do not achieve chemical resistant until they are cured properly, unless rustoleum is different i'd be cautious with the fuel  :o
I wondered this, too.  According to Rustoleum's tech data sheet, the paint will reach a full cure in 7 days.  I can say that I've tested the fuel resistance a bit when I spilled gas onto the engine when priming the carbs for the first time.  The paint didn't seem to bubble or have any lasting effect and I was able to wipe it up with out it transferring to the shop towel.  I'm sure it's time dependent to an extent.  Should I spill on the tank I'd be wiping it up PDQ.

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #83 on: Aug 29, 2016, 15:17:33 »
You've done a lovely tasteful job - worth preserving!
Thanks, jpmobius!

Allow me to be your guys' fuel resistance experiment :)  I'll be sure to post if I notice any troubles to save future folks the trouble.

Offline Maritime

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #84 on: Aug 29, 2016, 15:20:37 »
was the paint on the motor run through a heat/cool cycle? you should follow the can's instructions on that or you may have it fail down the road. Hopefully you do not run into any issues. If you can get the 2K clear in your neck of the woods and the proper respirator to wear while painting with it I would get it to be 100% sure you don't have issues.
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Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #85 on: Aug 29, 2016, 18:04:08 »
Alright, so this discussion has gotten me curious regarding fuel resistance…  I've done a bit of digging on this on the paint side from info provided by the two paint makers, Rustoleum and SprayMax, as well as the BASF Handbook on Basics of Coating Technology.  Pardon me while I reveal my true side for a moment…  (by day I'm a nerd)  I hope maybe I can help someone with this question regarding solvent resistance that isn't content without asking "Why?" as I personally dislike coming across posts where someone says, "well I've heard such and such to be true…" yet has no supporting data or evidence.  That's how rumors and misinformation spread :)

Fuel resistance comes largely from a paint's ability to be crosslinked via reaction from individual polymer chains which are easily dissolvable into a network of molecules all tied together that cannot be easily dissolved by solvents (ie. fuel.)

Rustoleum's Engine Enamel is an enamel paint that uses a "modified alkyd" as its base polymer.  Enamel paints will usually be crosslinked (ie. cured) via oxidative crosslinking.  This reaction needs oxygen (or another oxidizer) to be carried out.  This is largely why you want to spray lots of thin coats over a span of time.  If you spray too thick, the top of the paint will cure, or skin over, and prevent the lower layers from curing and they will remain soft and less chemically resistant.  Rustoleum's Engine Enamel tech data sheet lists their resin as a "modified alkyd" which is very unspecific, but the fact that it is regarded as modified tells me that it was better solvent resistance than a standard enamel as there are some chain modifications that be made to tune the resin to have higher heat and solvent resistance.  Their product is essentially a 1 part, where the crosslinking component comes from the air (oxygen.)

The SprayMax 2k clear coat uses acrylic resins as the base, which are mixed with isocyanates when you put the button on the bottom of the can to "activate" it.  When you do that, you're allowing the acrylic resins and isocyanates (the crosslinker in this case) to react with each other and start crosslinking to form a larger network of urethane polymers.  (BTW, isocyanates are very nasty and they are happy to react with your body as much as your paint's resins.  You can become sensitized to them with prolonged exposure and get a nasty, itchy skin rash so it's a really good idea to use respirators and keep the mist off your body.)  The 2k is a 2 part because the base resin and crosslinker in the same can, but separated until you puncture the divider and mix them together.

Ultimately, urethanes are going to be more resilient to solvent exposure than their enamel counterparts.  If you are able to get the 2k I'd say go for that for your gas tank.  If not, you should still be just fine with the Engine Enamel, but make sure you have a rag handy and wipe up any drips as quickly and gently as possible.  The enamel is designed for intermittent, quick exposure whereas the urethane can withstand exposure longer.

With regards to baking painted parts, there are a couple things to consider…  If the manufacturer specifically calls for heat curing then it's likely because there is a set of reactions that cannot occur without the elevated temperature.  In that case, do it absolutely!  The paint won’t be as strong without baking.
Otherwise, cooking a painted part that isn't designed with high temp. reactions will allow crosslinked bonds to form faster.  Reaction rates, in addition to drying rates, are very sensitive to temperature (see the Arrhenius equation) so higher heat will cure paint faster.
BUT, it doesn't necessarily mean it will be stronger than an unbaked part, and if you bake it too soon, it can lead to the lower layers being weaker.  This is because you can skin over the top of the paint before the lower layers have had a chance to react with oxygen.  Skinning over means you've crosslinked the top layer tightly, but when you do this, it becomes less permeable to oxygen which is needed to cure the lower layers.  In other words, if you paint it thick and put right in the oven it could actually take longer to cure.  Let me quote the BASF Handbook on Basics of Coating Technology which in reference to enamel paints says, "During oxidative crosslinking of the unmodified alkyd resins the forming film undergoes molecular enlargement caused by crosslinking, starting from its surface.  A reduction in oxygen permeability is an associated feature.  Good through-hardening therefore requires only slow surface hardening."
Again, this is why people say, "use many light coats."

Sorry for the length, but I hope this is useful for someone without a reactions background that has the question of gas resistance on 2k vs. enamel in the future and values content over opinions and hearsay.

Offline Maritime

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #86 on: Aug 30, 2016, 08:17:22 »
Nice write up Northish, good info and true, the clear yo have will be ok if you are careful and clean gas off right away and use water etc. but if you miss a dribble it will cloud up in the spots, I have personal experience with that, the 2K you can be pretty careless and not hurt it which is insurance I need when the bike is a heavy rider, if it is a once and a while I wouldn't worry as much.
The GL Rebirth: http://www.dotheton.com/forum/index.php?topic=68337.0
CX500 Low budget Bobber : http://www.dotheton.com/forum/index.php?topic=43617.0
"Beer makes you feel the way you ought to feel without beer" -Henry Lawson
"Beer is proof that God loves us and wants us to be happy." - Thomas Jefferson

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #87 on: Aug 30, 2016, 09:05:02 »
Nice write up Northish, good info and true, the clear yo have will be ok if you are careful and clean gas off right away and use water etc. but if you miss a dribble it will cloud up in the spots, I have personal experience with that, the 2K you can be pretty careless and not hurt it which is insurance I need when the bike is a heavy rider, if it is a once and a while I wouldn't worry as much.
Agreed - I think if I ever do a second, more fancy bike then I'll look harder for the 2k.

Offline Northish

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #88 on: Aug 30, 2016, 09:15:27 »
In other news, the carbs are rebuilt and back on the bike.  I've done as much research as I could on tuning and jetting to predict what jets and jet needle shimming I'd need to do to run my K&N's with pre-filters and the MAC 2-1 exhaust with a shorty muffler.

Main Jets - For main jets I've got 6 options, sizes 135 through 147, and these are actual Mikuni jets.  I am thinking that the 142.5 is where I'll start.
Jet Needle - When I took apart the diaphragms I noticed that there was no plastic spacer for me to remove, just a single metal washer about 0.5mm tall, so I am thinking a previous owner had fiddled with this already.  I was planning to do just this anyway so I left it as is.
Pilot Jet - Stock is a 17.5 and I also bought a 20 and a 22.5 just in case.  I've left the stock 17.5 in for now and will bump up if I run out of mixture screw travel.
Mixture Screw - I'll be starting with the screw 3.25 turns out

This tuning part has got me a bit nervous and I'm expecting the worst.  The bike hasn't started since Nov. 2015 and it now has new electronics, filters, exhaust, oil, plugs, gas, carb o-rings and main jets, and the carbs have been dipped and fully cleaned.
« Last Edit: Aug 30, 2016, 09:21:04 by Northish »

Offline danejurrous

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Re: 1981 Suzuki GS450L - Cruiser to Scrambler
« Reply #89 on: Aug 30, 2016, 17:22:15 »
This tuning part has got me a bit nervous and I'm expecting the worst.

Worst case scenario, doubt it would come to this with all your meticulous work, you have a killer looking piece of art to put up in the house.
81 GS750L - "it was my intention to "beat the 'L' out of it" - Buzznichols
79 xs650 Special II (chopping block)
82 xr500r
02 GSF1200S Bandit