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Cafe build seat issues by newbie for 91 Nighthawk

King_ME

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Hello all. This is my recently acquired 92 Nighthawk. I am planning on turning it into a cafe racer. However, I did notice that the frame takes a dip in the middle (unlike many of the older versions). This makes is a little harder to find a good seat. If you have any ideas on how to make the tank-to-seat position "seem" more level maybe by the way the seat cowl is made or not made.

I know I will be cutting the frame right behind the shocks and adding the ring. And I have actually found a guy who has done a pretty good job with his. I am just looking for any information anyone has to offer. I am looking for and older tank as well. Possibly a 450 or 650 tank. I like the style of the 200 tanks, but want something just a little bigger. I do like sleek and long though.

I guess I will post my progress here as I go. I have just started breaking it down and am going to tackle cleaning the carbs next.

Thanks for any help
 

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Might consider what happens to any side covers, those will not fit anything else pretty much.

If you give yourself up to a total seat redo the angle actually would make it look better. I do understand that most available seats have dead flat bottoms.
 
Could you please elaborate? I don't mind about the total seat redo. I would just like to tone it down a bit and for it to look as "flat as possible". There is one guy I've seen that has done a pretty good job with his......

https://www.youtube.com/watch?v=bf8uLl4cxwA


Although he is using the 200 tank. I will probably have to go to a 200 tank myself....just because (don't kill me.....I'm a newbie) I didn't realize that those tanks were soooo........hard to come by, and expensive even then!!!

Thank for your time!
 
You of course will be ditching the side covers, you see he made them himself there. You'll be doing the same, there is no blueprint for it and on your own there.

The tank is off a CB200 '74-'76, and they were pretty rare even back in the day. And hold virtually no fuel amount (2.9 gallon) at all, you might get 100 miles out of tank with a 750. I couldn't get 200 miles out of the 200 I had back then.

The OEM 200 petcock will be crazy stupid too small for that engine as well, you may well have fuel supply issues. I have a CB550F with same petcock and it gives problems on those if you run out of gas, the carbs have trouble priming again. Around '81 or '82 Honda started realizing the petcock commonly used was giving all sorts of fuel issues on the bigger 1st gen DOHC engines and began making them with much bigger fuel passages in them. Before that almost everything they made used same basic petcock fuel hole size.
 
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WOOOW!!! Thanks for the info. Yeah, I knew that tank only held 2.9, which is why I didn't want it in the first place. I didn't know about the petcock situation.

I wanted something bigger, but along the same lines as that tank. I really like the 650 super sport tanks....or anything close to it. But those were even harder to find than the 200.........which discouraged me a bit.

So.......what you're saying is, I need to stick to something at least in the 80's regarding the tank. I mean, i'm pretty good on keeping the tank full, but wouldn't want a slip-up to be more costly (time or money wise) than it should.

Thanks amc!
 
Hey, 500+ lbs. is a b-tch to push down a highway, BTDT.

Year doesn't matter, I was surprised to find the 200 tank actually didn't look out of place there. Use what you want but go in eyes wide open.............
 
Yep.......the tank looks good. Didnt look too small or anything. I think the seat is a little longer and of course thinner, and the tank a little shorter and thinner (no peanut). He still had a little room in between the tank and seat. But not enough for me to be bothered by it.

So, I will be sure to make sure the petcock' feul passage is big enough to accomodate the engine/carb size? And know what problems may be caused by switching....

If you come across any tanks with that style.....or the super sport style....think of me! LOL

Onward and upward. I'll be cleaning the carbs this weekend. They have gotten a little dirty and it won't start now. First things first.

Thanks for all the info!
 
Question..........do you think/know if the older 750 tanks would work (70's)? I know you said they reconciled in the early 80's somewhere about. But wondering if there were any problems with those tanks petcocks/engine compatability? Or do you just suggest to keep looking for a little later models, even if they are a bigger size tank?

Thanks in advance......
 
Pretty much all those early tanks got the small petcocks, but power levels not high enough to begin to f-ck them up yet..........the tanks may be too short anyway, the later frames have longer wheelbases and the tank area stretched a little too.

Once you begin to mod like where you're going you can use ANY tank and simply get a better bigger petcock installed by welding a different bung there.

FYI, flipside of bigger petcock on later models was that Honda then began to have issues with hydrolocking of motors due to fuel leaking with bikes on sidestands, the owners not turning petcocks off. Honda was forced to install the vacuum demand fuel valve the later ones use. So, change something and get bit, the way physics work.
 
Thanks amc49! I greatly appreciate your taking the time to address my questions with great information and knowledgable answers. When I come across a good tank.....I will most likely reach out again!!!

Thanks again-
 
I made a template out of cardboard and traced it onto a sheet of aluminum and bent it in a brake..

Very useful to have the frame close as you don't want to over do the bend.. nice and easy till it matches the frame well... Would definitely advise getting the tank figured out and the loop installed before even attempting the seat!

I ended up skinning the stock seat foam off really carefully to re-use with an old filet knife, then used spray adhesive to stick it to the aluminum... Make sure you get any hardware for securing the seat before you glue the foam on... once I had the foam on I rough cut with serated knife, then used a wire wheel on a die grinder to finish shape the seat contours.. be careful with this as it will try to grab the foam.. little at a time and good idea to keep your hand on the seat as a guide of sorts.

Remember when shaping the seat you need to account for the thickness of 'finish foam' which is usually 1/4 to 1/2" and the layer of the leather itself... I dulled up the sharp edge around the seat and got some super thin door edge guard from auto parts house to make sure it wouldn't slice through the leather after it was affixed.

I had a guy make the seat out of some specific leather I had (charged me 50 bucks) but I'm sure you can use just about anything or get a cheap seat online for the skin..

Once I got the skin I started at the back and started drilled holes and simple riveted it in.. All in all I was happy with it..


Photo Aug 07, 11 11 20 AM.jpgPhoto Aug 10, 1 12 48 PM.jpgPhoto Aug 11, 2 15 15 PM.jpgPhoto Aug 16, 1 04 04 PM.jpgPhoto Aug 29, 2 46 39 PM.jpgPhoto Aug 29, 2 47 21 PM.jpg
 
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I was told to use simple rough sandpaper to finish the shape and I thought the person crazy but it works like gangbusters! Personally I'd be terrified of suddenly eating too much foam with anything turning there.....................but a sanding disc would work there too if it works by hand.
 
Yeah you definitely have to be careful with any power tools.. I actually used wire wheel in die grinder and a cutoff wheel, have to be very ginger to keep it from getting away from you.. i had a lot to take down in my case didn't want to mess around all day.. finish foam on the leather smoothes out imperfections really well
 
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