1981 Suzuki GS450L - Cruiser to Scrambler

adventurco

Nick Ol' Eye
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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 :eek:
 

jpmobius

where does this go?
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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!
 

Northish

If you know what you're doing, you're not learning
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adventurco said:
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 :eek:
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.
 

Northish

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jpmobius said:
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.
 

Maritime

Well-Known Member
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.
 

Northish

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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.
 

Maritime

Well-Known Member
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.
 

Northish

If you know what you're doing, you're not learning
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Maritime said:
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.
 

Northish

If you know what you're doing, you're not learning
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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.
 

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danejurrous

New Member
Northish said:
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.
 

Northish

If you know what you're doing, you're not learning
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danejurrous said:
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.
Haha! You hit the nail on the head danejurrous... I've been telling people essentially that; that I'm just making very expensive garage art. I suppose I could try to get it in the house somewhere though... :eek:

DannyMotor said:
I absolutely love how this is coming out! Great work!
Thank you, DannyMotor :) That means a lot. I see you've had to mess with 4 carbs on your GS. I can't even imagine... The two on mine are intimidating enough. :p
 

5ivemoto

New Member
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Very cool project. Really dig it. The rattle can paint job looks stellar nice tape lines. Just all around good stuff. Kudos
 

Northish

If you know what you're doing, you're not learning
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5ivemoto said:
Very cool project. Really dig it. The rattle can paint job looks stellar nice tape lines. Just all around good stuff. Kudos
:) Thx 5ivemoto - I appreciate the kind words.

The cosmetics of the bike are pretty much done, so at some point I hope to get some nicer shots outside of the garage. I'm forcing myself to hold off on final pictures because to me it still needs to run correctly before I can post "done" pictures. Tonight I'll be starting her up and seeing just how much of a mess I've got on my hands to tune up. I've never tuned a carb before other than adjusting the idle on a weed-whacker, so again, expecting the worst and may be posting lots of frantic "What does this sound mean?!?!" posts.

For starters, where does one plug their laptop into the carbs at to tune them?!?! ;)
 

DannyMotor

Blood, sweat and beers.
Northish said:
Thank you, DannyMotor :) That means a lot. I see you've had to mess with 4 carbs on your GS. I can't even imagine... The two on mine are intimidating enough. :p
Yup! That's why I'm only working on parallel twins from now on! :)
 

Northish

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This update has its ups and downs... or rather downs and then ups :)

I was able to get some gas in the bike and start it for the first time since January 2016. It was a little sluggish to get going at first and had to put it on full choke to get it to kick over. It did fire up though... well, at least half of it did. It sounded pretty rough and I quickly found out that the left cylinder wasn't firing at all.

I had a sneaking suspicion that it had to do with the way the RPM pick-up wire from the Koso digital gauge was wired into the signal wire going to the left cylinder coil. The pick-up wire for the gauge is actually 2 wires, one black that was supposed to grounded and the other connected to the signal wire coming from the ignitor. The Koso directions were tough to decipher and I was a bit suspicious about grounding the signal wire. Sure enough as soon a I disconnected the ground the cylinder started working and the gauge started to display RPM info. Got lucky there figuring that out right away; boy was I nervous it was something else.

It was still running pretty rough after that. I wasn't really able to take it off choke even once it warmed up. I did a lot of messing with the mixture screws and was able to get it off the choke by turning them out a fair amount. But, then I was no longer able to give it any throttle whatsoever. It would just instantly die. I could put the choke on and then quickly twist the throttle and it would get up and out of the low end, but I couldn't slowly roll out of the low end. It was very frustrating. Very very frustrating.

Settings at this point:
Mixture screw - 3.25 turns out
Pilot jet - 17.5 (stock)
Float height - 23.5 mm
Jet needle - plastic spacer removed, one 0.5 mm washer in its place
Main jet - 145.2

Parts:
Mac 2-1 exhaust, shorty muffler, K&N pods with Outerwears prefilters

I decided to just pull the carbs back out and tear them apart since I wasn't getting anywhere with the adjustments I could make. They were acting like the pilot circuit was plugged or something very wrong. I've seen a lot of discrepancy in float heights reported for these GS450. Clymer says 22.4 mm, others say 26.6 mm. I ultimately set the float heights to 26.3 mm and upped the pilot jets to 20 just to see where that would put things. I was pretty much grasping at straws at this point.

Settings after changes:
Mixture screw - 2 turns out
Pilot jet - 20
Float height - 26.3 mm
Jet needle - plastic spacer removed, one 0.5 mm washer in its place
Main jet - 145.2

I got dead lucky. I'm pleased to say the bike started up much much more easily :) It required a little choke to get warmed up, but once warmed I was able to take it off and it fell into an idle at about 900 rpm. I did a few throttle blips, which were impossible before, and it indicated a little rev hang which I read to be too lean. Working on the mixture screws ultimately brought the idle speed up to 1,200 which is where it should be factory. When blipped, it responded very well. I ultimately found that 3.75 turns out on the mix screws was best. Getting close to going up another pilot jet size. I wouldn't normally confound things by changing more than one variable but I was frustrated. Feeling much happier as I can work from this base.

Final settings tonight:
Mixture screw - 3.75 turns out
Pilot jet - 20
Float height - 26.3 mm
Jet needle - plastic spacer removed, one 0.5 mm washer in its place
Main jet - 145.2

Ultimately, I intend to follow the standard tuning steps of find main jet first at full throttle, then move to jet needle shimming in mid range and finally pilot and mix screws. At the moment though, I need to get insurance and registration set up. Helmet is being delivered tomorrow as well as a license plate bracket and mirrors :) Hoping I can get out and ride yet before the frost comes!
 

Northish

If you know what you're doing, you're not learning
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Everyone likes pics and videos over text, so here's where things stand after the carb work last night:
https://youtu.be/oGBFxHXHx0s
 

Maritime

Well-Known Member
Nice, a ride will tell you a lot more for your jetting but sounds like you have a good start.
 

Northish

If you know what you're doing, you're not learning
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I've spent some time balancing the carbs. They weren't too far off but there was a slight difference. Attached are before and after pictures of the gauge readings.
 

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Northish

If you know what you're doing, you're not learning
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So, I've been having some trouble getting the bike to run right at partial throttle openings. It would sound like it was going very rich and would start running really rough/stumble and lose power. Not a very reassuring thing to have every time you are pulling away from a stop light.

I went looking for some advice on gsresources.com and a couple knowledgeable folks there recommended looking at the slides/needle area and not the pilot circuit. Here are the results and what I found to be the issue:

I've broken down the carbs again tonight after work and gone through everything again. I focused on the slide/jet needle/diaphragm parts. The diaphragms showed no holes when backlit. The slides were buttery smooth upon lifting and dropping and lifted when presented with air. The jet needles were genuine Mikuni non-adjustable 4C2's (somewhat unfortunately) and showing no wear.

The issue was completely my fault and ended up being the C clips in the slides not being seated correctly. I thought I had gotten them below the ridges but they were slightly above. This caused the jet needles to be too high up which was flooding the carbs with gas at partial throttle when the transition off the idle circuit was occurring.

I'm happy to report that the low throttle stumble is gone and I took the bike on the longest ride I've ever had with it (which was about 1 mile.) It seemed to be a hair lean, with a little rev hang when blipped, but I am happy to have a base I can work with.

And a picture of me smiling behind the helmet :D
 

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