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Discussion Starter · #145 ·
The part numbers that I highlighted in green are for an 86 PRS and would be applicable to the entire chassis.

I did pick up the chassis. It is home in my garage but I had no time to take all the necessary measurements. I will have a better opportunity to assess what it is and how it might be used for my 86 Plus.

Here is what I do know.
It is a 87 MX-LT chassis. (It was bought to replace the chassis of an 87 MX-LT but never used.)
There is no VIN stamped on the tunnel. (It has the recess and the rivet holes to transfer the VIN plate.)
It has the MX-LT aft bulkhead with the welded-on MX-LT bumper but the tunnel also has the boltholes for the bolt-on bumper. (86 Plus has the bolt-on bumper configuration.)

I did take some measurements lengthwise and the 87 MX-LT tunnel is the same length as the 86 Plus. The tunnel lengths are the same! I measured front to back, in total, to seat boltholes, to gas tank studs, to cooling cutouts. I did not measure the rear PRS suspension boltholes as I assumed they would be different and relocating them would be easy enough. I did not measure exact width of the tunnel, but I should have. I will do that when I get off duty. If the tunnel is a different width, then the birdcage will also be different and I am back to square one.

Side note:
1985 Plus and MX use the same chassis. Then in 86 the Plus and the MX use different chassis.

I will post some picts later today.
 

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Discussion Starter · #146 ·
I measured the tunnels every way and in every direction. The 87 MXLT tunnel matches up to the 86 Plus tunnel with the exception of the aft bulkhead. The MXLT tunnel and front frame have some minor corrosion and powder coat peeling.

My plan remove the 40 rivets and the tunnel from the front frame of the MXLT. Clean and prep the front frame where the powder coating has peeled off and spray paint those areas. Rivet the original tunnel to the frame.

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91 Plus, 93 Mach 1 and 97 Mach Z.
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I am far from sure about the exact differences during the 1986 model year, but I did little bit of an investigation regarding the PRS front frames in general. Searching for something completely different, I stumbled across the brand new one with part number 580507100. This is the spare part number for all 1989 models and I was - of course - keen to find out if I can use it for some other model year. I started a thread regarding this topic and I have also been digging little bit deeper since.


In summary - it's a complete mess...I don't think two consecutive years share the same part number, indicating there are some kind of small differences between each year. At the same time, some years have individual part numbers for each model. At the same time, some years have the same part number for all models...The one I found is not painted nor powder coated, where some years before as well as after 1989 appear to have been delivered painted or powder coated...

Asking some mechanics and some other people that were around during the 80's, I have non-confirmed indications there have been small differences in:

The footrest loop introduced for 1991.
Different silencer brackets.
Different positions for fuel pump mounting holes.
Different positions for tunnel mounting holes.
Different trailing arm mounting angles (depending on ski stance).

I don't think anybody except for the design engineers from back in the 80's will know for sure, so the best advice is probably to measure what you have got as well as your donor carefully.
 

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Discussion Starter · #148 ·
My probable buyer stopped by to take a look at the options. He would rather have his welder friend take care of the rotted frame tubes and preserve the original tunnel and frame. I'm good with that. The chassis that I acquired is going to the crusher.

Easy.......Just kidding. I will return it with a big "thank you anyways".

This sled has been a real PIA but well worth it. Suspension is ready for installation.

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Hey Curta,
Great work its going to look awesome.

Do you use a rivet removal tool? Or do you do the old fashion drill bit method? I'm jealous of how clean you can take out old rivets.

Can't wait to see the finished product!
 

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Discussion Starter · #155 ·
Hey Curta,
Great work its going to look awesome.

Do you use a rivet removal tool? Or do you do the old fashion drill bit method? I'm jealous of how clean you can take out old rivets.

Can't wait to see the finished product!
I drill them out. Sharp bit and holding the deformed end with pliers helps. If the bit bottoms on the pull pin inside the rivet, use a small punch to set the pin down further.

For the installation I used steel painted rivets to join the tunnel to the front frame and aluminum rivets (steel pull pin) for the heat exchangers.
 
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