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Papa Lazarou
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lcjohnny
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PostSubject: Broken bodywork   Broken bodywork Icon_minitime1Fri Aug 12, 2022 10:53 am

On my GRiSO the front of the left hand side-panel had a crack in it where it goes over the back "leg" of the fuel tank,

The fuel tank legs are spread too wide and need to be squeezed in a bit for the bolts to go in, I think that as the bolts are removed and they spring out they have loaded up the side-panel just where it is screwed in tight.

Well the top bit of the plastic fell off about 3 months ago and stayed trapped under the seat ( cheers ) so i cleaned it up and used Araldite (2 part epoxy) to fix it back together.

It has just broken again  scratch
- the Araldite had not bonded to the black plastic so i could pick it off with an engineers scriber,

Does anyone have experience with a glue that actually bonds to the side panel plastic?

Picture of broken area
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paulbrice
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Aug 12, 2022 1:07 pm

I think the 'problem with pure epoxy resin (or filler) is that the join is low area (relatively) unless you lay some kind of matrix that holds the bits together & sometimes (especially if there's a fitting in the centre of the break) you need to make the solution bigger and join it where there's more/less stressed surface  - can either be mesh, bolts or shaped bits of steel/other stuff, also needs lot of scratching/sanding to key the resine that hold the matrix to the base.

I posted elsewhere but I used araldite (epoxy resin) on V50-3 side panels & plastic filler with mesh on instrument binnacle. I now use Big Boy filler (with some kind of reinforcement) everywhere including wooden doors and windows !.  I'd also think about fibreglass (with reinforcement for panels like GRiSO near the bolt holds) - but needs massive overlap to hold together.

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lcjohnny
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Aug 12, 2022 3:25 pm

to be honest, at first i thought that
"Big Boy Filler" was a piss-take What a Face

But it looks good

My current thoughts are to glue the piece back on with JB weld
Then fill as needed.
Fnally to have that front piece of the sidepanel loose with a thin rubber pad behind it so it can be pushed out when the tank is unbolted.
If it works i may stick a screw head into the hole after i paint it
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Aug 12, 2022 5:31 pm

The sort of damage ICJ has is very, very common. If a GRiSO falls over one has to be extremely careful when picking it up a almost any pressure applied to the underneath of the tailpiece seems to result in that sort of breakage.

I have three or four tailpieces in my 'Mountain of Munt' and I think three of them have exactly the same damage. The bodywork that is off for painting for the GRiSO Tourismo has a similar missing chunk at the top of the tailpiece. I'm hoping it doesn't look too obtrusive, it didn't when it was green.

When I repainted my original G8 yellow last year I actually sought out and purchased one of what I suspect will be one of the last brand new tailpieces in captivity. The price was eye watering! Repair has to be possible. Perhaps filling with plastic weld and then careful carving back before finishing with abrasives would work? I'm hopeless at this sort of stuff though. I've never been good on cosmetics and bodywork.

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Steveo
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Aug 12, 2022 8:10 pm

lcjohnny wrote:
On my GRiSO the front of the left hand side-panel had a crack in it where it goes over the back "leg" of the fuel tank,

The fuel tank legs are spread too wide and need to be squeezed in a bit for the bolts to go in, I think that as the bolts are removed and they spring out they have loaded up the side-panel just where it is screwed in tight.

Well the top bit of the plastic fell off about 3 months ago and stayed trapped under the seat ( cheers ) so i cleaned it up and used Araldite (2 part epoxy) to fix it back together.

It has just broken again  scratch
- the Araldite had not bonded to the black plastic so i could pick it off with an engineers scriber,

Does anyone have experience with a glue that actually bonds to the side panel plastic?

Picture of broken area
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It will depend very much on what plastic the part is made from. If the part is large enough it will be marked on the inside somewhere,
the side panel of my Breva is Polypropylene and so is marked >PP<.

This is bad because PP is a low surface energy plastic and very hard to adhere to.
The only truly robust fix is to use fasteners and some form of bracket or to plastic weld the parts together, unfortunately this will lead to a lot of finishing work if the surface is visible. If you don't want to, or can't do this, use Pauls solution and maximise the surface area where of your reinforcement material is glued to the plastic.

If the plastic is ABS you are in luck as you can obtain a good bond using a solvent which if applied correctly will weld the parts together. There are plenty of ABS glues available especially at hobby shops. If you need to build up an area or replace missing material dissolve ground up ABS in the solvent which will turn into a snot like consistancy and eventually turn into rigid ABS

Good luck and experiment on something "unimportant" first

Steve

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Buellbloke
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Sat Aug 13, 2022 11:43 pm

Bad design, certainly a common thing, mine although not broken is a bit naughty where the tank meets the side panels at that point, sort of sits on it. Mates yellow peril came like that broken there.
Him not having the broken part means living with it, it was cheap and cheerful though fully GRiSO ghetto maintained as all grease points serviced, even beetle mapped we're assuming Shocked

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BrianD
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Tue Aug 16, 2022 8:45 am

In the past I have used a bit of fine wire mesh and used a soldering iron to melt into the plastic (on the back) - may be worth thinking about.

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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Tue Aug 16, 2022 8:57 am

I am listing all of the plastic types used on GRiSO bodywork
has any one got the tank off so they can read the plastic resin code (big letters in a triangle design)?
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Tue Aug 16, 2022 10:21 am

NOTE Earlier I wrongy stated PBT was Polycarbonate, it is Polybutylene Terephthalate a polyester

Here I have listed the plastic resin codes I have found on various bodywork parts of my 2008 GRiSO.
I also list the results of my internet research on how to bond or glue them but if there are any industrial chemists or others with better knowledge - please correct me


Bodywork rear Plastic resin code PBT made of:  Polybutylene Terephthalate
 Nb this is known to be hard to join or bond because PBT is a low surface energy polyester
To bond it
Firstly wash and degrease with soap or isopropyl alcohol but do not roughen the surface
Then in order of reported strength of the joint
   • Nitrogen/Hot air welding
   • Thermosetting acrylic adhesive
   • Polypropylene adhesive or other "low surface energy adhesive"
   • 2 part flexible epoxy hold 5-10min FS in 96hr (in my experience this does not bond)
   • specialised cyanoacrylates with a surface treatment or specialised primer e.g. Loctite 401 Prism Instant Adhesive, with Loctite 770 Prism primer.
   • RTV Silicone for large areas
 

Fuel tank and Horn cover plates Plastic resin code PA6  made of: Nylon 6 a Polyamide
Nb this is known to be hard to join or bond
To bond it
Firstly wash and degrease with soap or isopropyl alcohol, micro roughen surface e.g wire wool
Then in order of reported strength of the joint
   • Thermoplastic airless fusion welding
   • Plastic specific cyanoacrylate: wet edges - hold 1min Full Strength in 12hr
   • Two-component Polyurethane adhesives
   • 2 part flexible epoxy hold 5-10min Full Strength in 96hr
   • RTV Silicone for large areas


Wings Plastic resin code  PC+PBT made of: Polycarbonate/Polybutylene Terephthalate a polyester mix or ‘alloy’.
Nb this is known to be hard to join or bond because PBT is a low surface energy polyester
To bond it
Firstly wash and degrease with soap or isopropyl alcohol but do not roughen the surface
Then in order of reported strength of the joint
   • Nitrogen/Hot air welding
   •Thermosetting acrylic adhesive
   • Polypropylene adhesive or other "low surface energy adhesive"
   • 2 part epoxy hold 5-10min FS in 96hr (in my experience this does not bond)
   • Specialised cyanoacrylates with surface treatment or specialised primer e.g. Loctite 401 Prism Instant Adhesive, with Loctite 770 Prism primer.
   • RTV Silicone for large areas


Front mudguard Plastic resin code >PP< made of:  Polypropylene
Nb this is known to be very hard to join or bond
To bond it
Firstly wash and degrease with soap or isopropyl alcohol but do not roughen the surface
Then in order of reported strength of the joint
   • Hot air weld with FiberFlex® Universal Rod
   • Polypropylene adhesive or other "low surface energy adhesive"
   • 2 part flexible epoxy hold 5-10min FS in 96hr
   • RTV Silicone for large areas

references
PBTs bonding PBT
Cyanoacrylates Loctite design guide
Pragmatic guide to plastic car body repairs (with a hot air welder) Polyvance plastic repair book


Last edited by lcjohnny on Sat Sep 03, 2022 3:43 pm; edited 7 times in total (Reason for editing : factual corrections from Steveo)

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Papa Lazarou
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Tue Aug 16, 2022 11:13 am

I have a brand new Rosso tailpiece with decals....
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Wed Aug 17, 2022 10:43 am

Papa Lazarou wrote:
I have a brand new Rosso tailpiece with decals....

Whats one of those look like?
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steveb
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Wed Aug 17, 2022 12:09 pm

super glue with baking soda sprinkled over it bonds a lot of un glue able plastic
Steve
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lcjohnny
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Wed Aug 17, 2022 12:18 pm

steveb wrote:
super glue with baking soda sprinkled over it bonds a lot of un glue able plastic
Steve

Any idea how?

I have read that acid can be used to "activate" the surface of some of the olefin polymers like polypropylene and nylon so that adhesives will bond. Does baking soda do the same?
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Thu Sep 01, 2022 11:50 pm

Hi Jon,

Just came across this post now. I don't know if you have solved it meanwhile...
I also broke that corner of the panel when the bike accidentaly falled on the side while changing the tires in the tire shop.
I used the same recipe mentioned by Steve: Super Glue sprinkled with baking soda. In several layers...
So first I glued the chunk to the panel (fracture surface) and then I applied a layer of glue on the inner surface of the panel around the crack and sprinkled with baking soda. Waited for a bit (it hardens real fast) aplied some more glue and sprinkled again. Just make sure the volume created doesn't colide with other parts.
It's been a couple of years now and it is still holding...
But in your picture it looks like the taking is applying a lot of pressure on that corner of the pannel...You have to sort taht out too, or nothing will hold. Maybe you need a washer under the panel, on the screw hole....or file that turned lip a little bit...
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Sep 02, 2022 12:45 am

I had the same thing happen to mine on the right hand side. I have repaired and bought 2 sets of stickers that are not give aways by no means cost wise. Finally, with mine it seemed the Allen fastener head itself needed ground down to smaller diameter and then only tightened a bit with lock tight just to hold bolt on. So far so good but crack reoccurred but didn't tear 1200 sticker. Pain in the arse and a fuck all at this point.
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Sep 02, 2022 4:40 am

I have found that PBT actually stands for a different plastic - Polybutylene Terephthalate
have corrected the big post above

this is an olefin plastic like polypropylene so low surface energy and many glues will not bond to it
I have ordered a couple of 2 part adhesive for low energy plastics
TECHNICQLL ADHESIVE GLUE GEL FOR PP Polypropylene PE Polyethylene PTFE
and
Bondloc B3294 Plastic Weld High Strength

will report on which works best

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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Sep 02, 2022 6:30 am

Sorry a bit late to the party on this.
Is the root cause of the problem a result of the fuel tank deforming due to the ethanol content in modern petrol?
Would it be possible to jack the rear of the tank up 2 or 3 mm to restore the factory gap and remove the pressure from the between the edge of the tank and retaining screw.
With correct filler rod, PBT welds well (popular for car bumpers). A skilled repair centre should be able to complete a strong spot repair and blow the colour back over for not a huge cost.
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Sep 02, 2022 7:01 am

eeyore wrote:
Sorry a bit late to the party on this.
Is the root cause of the problem a result of the fuel tank deforming due to the ethanol content in modern petrol?
Would it be possible to jack the rear of the tank up 2 or 3 mm to restore the factory gap and remove the pressure from the between the edge of the tank and retaining screw.
With correct filler rod, PBT welds well (popular for car bumpers). A skilled repair centre should be able to complete a strong spot repair and blow the colour back over for not a huge cost.
Hi
The bike has not had any more ethanol than E5 for the last 2 years (about 110 tankfuls)

The two extensions at the back of the tank go to the mounting points and i have always had to squeeze them in to get both mounting bolts to line up.

If i jacked up the tank by about 7mm it would clear the side panels - but would look awful and possibly not fit under the seat?
I think that after it is repaired i may leave the front mounting point on that side unattached with a fake bolt head glued in place

I will explore bodywork welding places thanks

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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Sep 02, 2022 11:46 am

lcjohnny wrote:
eeyore wrote:
Sorry a bit late to the party on this.
Is the root cause of the problem a result of the fuel tank deforming due to the ethanol content in modern petrol?
Would it be possible to jack the rear of the tank up 2 or 3 mm to restore the factory gap and remove the pressure from the between the edge of the tank and retaining screw.
With correct filler rod, PBT welds well (popular for car bumpers). A skilled repair centre should be able to complete a strong spot repair and blow the colour back over for not a huge cost.
The bike has not had any more ethanol than E5 for the last 2 years (about 110 tankfuls)

The two extensions at the back of the tank go to the mounting points and i have always had to squeeze them in to get both mounting bolts to line up.

If i jacked up the tank by about 7mm it would clear the side panels - but would look awful and possibly not fit under the seat?
I think that after it is repaired i may leave the front mounting point on that side unattached with a fake bolt head glued in place

I will explore bodywork welding places thanks


That was my final try to help avoid another Crack was just cutting the threaded side of body fastener off and gluing. I think it's a safe bet that it's the fastener fully threaded that puts the stress on that little top edge of that tail piece. Almost seems that the jig when welding frames was off a bit as far as that particular screw set. Sure seems like there's alot of us....

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Steveo
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Fri Sep 02, 2022 9:58 pm

Hi Jon
A couple of points, one PBT is not a olefin, it is a polyester and apparently can be glued with a range of Loctite adhesives according to this jolly little document Loctite Guide

The tank is Nylon 6 and although the above doc lists Polycarbonate as being suitable for superglue I would not trust it. Polycarb mouldings can end up have high moulded in stresses which resolve into cracks with the application of some adhesives including superglue, PC/PBT blends are probably fine.

As you can see I spend far to much time with plastic injection moulded parts.

Cheers

Steve

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lcjohnny
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Sat Sep 03, 2022 1:00 am

Steve that is very good information
I have already incorporated it into the long post - please check for accuracy.
Interesting point about the use of specialised surface-treatment primers for specialised cyanoacrylates thank you.
Any other errors or omissions - please say

2 questions
(1) One of the papers that i had found specifically stated that roughening PBT does not improve adhesion and may worsen it - what do you think?
(2) would you agree with my finding that 2 part epoxy is unlikely to bond with PBT

Jon

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paulbrice
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Sat Sep 03, 2022 3:43 am

Guessing you found same but this is defo interesting one...

Repair Plastic book

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lcjohnny
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Sat Sep 03, 2022 7:08 am

paulbrice wrote:
this is defo interesting one...

Repair Plastic book

That is a really brilliant resource

except...

Now i want one of these plastic welder

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lcjohnny
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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Sat Sep 03, 2022 10:11 am

Gootzibird13 wrote:
That was my final try to help avoid another Crack was just cutting the threaded side of body fastener off and gluing. I think it's a safe bet that it's the fastener fully threaded that puts the stress on that little top edge of that tail piece. Almost seems that the jig when welding frames was off a bit as far as that particular screw set. Sure seems like there's alot of us....

Another way of stopping the damage might be to cut the bottom out of the well in the bodywork and put the screw into the frame holding a rubber collar.

That would give fore and aft location to the bodywork and damp out any buzz but allow the tank to push it the bodywork out without damage when the tank bolts are undone.

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PostSubject: Re: Broken bodywork   Broken bodywork Icon_minitime1Sat Sep 03, 2022 11:28 am

I tried that with a dremmel it was another attempt. Keep in mind that I bought another new tail piece after first initial Crack. With the new I carefully reinforced and beefed up with 2 part epoxy in addition to dremmel out the upper part of attachment indention to allow for stress movement ect. It just likes to take the weight of the seat force upon itself it seems to further the problem. If it weren't for the difficulty (time)of removing tailpiece I would give it another shot. GRiSO is approaching 65,000 and she has subtle dings elsewhere. Doesn't mean I don't keep it polished with ACF 50 after every cleaning though....Just love the bike, and as many others here, will not be selling it. Character flaws and all. Good luck with your repair and I did download plastic repair and ID manuals. Awesome info!
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