82 750S jetting

From a simple dustcap to a full on turbo-nitrous breathing monster.
If you have any questions, here's the place to ask.
Post Reply
jimbo22
Posts: 24
Joined: Tue Oct 20, 2015 12:26 pm
Location: Warsaw, Poland

82 750S jetting

Post by jimbo22 » Thu Oct 22, 2015 9:13 am

Hi,

Does anyone have any experience regarding jetting the katana?

I bought mine with Cones installed (and some 4-1 italian exhaust). The bike run good, so I thought that cones + exhaust, got the dyno and tuning therapy. But as I inspected the carbs - jets are stock...

there is no kit from Dynojet or Factory pro... So... Any tips? starting point? that would save some time as a starting point? :)

Thanks in advance....

User avatar
Pedda
Club Member
Posts: 1488
Joined: Mon Oct 25, 2010 11:21 am
Location: Stadtlohn, Germany
Has thanked: 51 times
Been thanked: 192 times

Re: 82 750S jetting

Post by Pedda » Fri Oct 23, 2015 1:40 pm

Is that Italian exhaust a Termignoni? Very common back in the day. Nice sound, a little flat spot revving around 4 - 4,5 k.
There was no rejetting required as long as you ran the stock air box and filter. Maybe you got a pic of that exhaust?

Do I get you right - you already ran your bike in the described setting and it ran fine? What about the sparks? How did they look like? Any white(-ish) debris around the exhaust outlet?

User avatar
Uncle Bob
Site Admin
Posts: 1748
Joined: Mon Nov 26, 2012 12:05 pm
Location: Norwich, Norfolk
Has thanked: 592 times
Been thanked: 227 times
Contact:

Re: 82 750S jetting

Post by Uncle Bob » Sat Oct 24, 2015 4:04 pm

I found this Jetting Guide on the SOHC/4 Owners Forum useful as a starting point on my 400:

http://forums.sohc4.net/index.php?topic=58112.0

jimbo22
Posts: 24
Joined: Tue Oct 20, 2015 12:26 pm
Location: Warsaw, Poland

Re: 82 750S jetting

Post by jimbo22 » Mon Oct 26, 2015 9:27 am

hard to believe in such a linear progresion of sizing... + there is not even 1 word, about needles... so it looks like a pretty useless tutorlial if You want to do things the correct way... but it's a interesting read.

I was hoping to get feedback for this particular model though:)
Last edited by jimbo22 on Mon Oct 26, 2015 10:22 am, edited 1 time in total.

jimbo22
Posts: 24
Joined: Tue Oct 20, 2015 12:26 pm
Location: Warsaw, Poland

Re: 82 750S jetting

Post by jimbo22 » Mon Oct 26, 2015 9:31 am

Pedda wrote:Is that Italian exhaust a Termignoni? Very common back in the day. Nice sound, a little flat spot revving around 4 - 4,5 k.
There was no rejetting required as long as you ran the stock air box and filter. Maybe you got a pic of that exhaust?

Do I get you right - you already ran your bike in the described setting and it ran fine? What about the sparks? How did they look like? Any white(-ish) debris around the exhaust outlet?
will check the markings on the exhaust today.

I know the bike runs good, as my friend sold it to me. He said he made 200 miles on it before taking it apart. the spark plugs look ok.

As I wrote - I was sure that after puting the cones on, and custom exhaust - the original owner must have made some carb changes. But it turned out that he didnt'. In this case I can't believe that it doesn't run lean. Will have to figure it out by myself soon :)

User avatar
Uncle Bob
Site Admin
Posts: 1748
Joined: Mon Nov 26, 2012 12:05 pm
Location: Norwich, Norfolk
Has thanked: 592 times
Been thanked: 227 times
Contact:

Re: 82 750S jetting

Post by Uncle Bob » Mon Oct 26, 2015 6:56 pm

jimbo22 wrote:hard to believe in such a linear progresion of sizing... so it looks like a pretty useless tutorlial
That's why I said "starting point" ;) That was the best I could find really when I needed to get an idea for jets on my 400 - you gotta start somewhere some how.
Nigelkat in getting his 550 to run right, had 19 dyno runs in the end with carbs tweaks inbetween - http://www.katanaownersclub.co.uk/forum ... &start=320

Re: the 400: Even up on 2 jets sizes it was better from 7k rpm, but around 10k starts to lack power again, so not sure whether to go up another jet size or raise the needle by one notch which was a possible recommendation on here.

Rob

callyboy

Re: 82 750S jetting

Post by callyboy » Mon Oct 26, 2015 9:56 pm

This is from dans recent dyno run. does that help?

Pete
Attachments
12179659_10156252630630085_888638367_n.jpg

jimbo22
Posts: 24
Joined: Tue Oct 20, 2015 12:26 pm
Location: Warsaw, Poland

Re: 82 750S jetting

Post by jimbo22 » Tue Oct 27, 2015 11:06 am

on full throttle and high rev, needle is not important. its fully open anyway - so ONLY main jet is the topic here.

jimbo22
Posts: 24
Joined: Tue Oct 20, 2015 12:26 pm
Location: Warsaw, Poland

Re: 82 750S jetting

Post by jimbo22 » Tue Oct 27, 2015 11:13 am

callyboy wrote:This is from dans recent dyno run. does that help?

Pete
Thanks. It helps a little. proves that pods don't kill the engine totally... i can see that there is only 1 main jet size up installed. Do we have more dyno chrts? to see the 1/4,1/2, 3/4, full throtlle power band?

callyboy

Re: 82 750S jetting

Post by callyboy » Tue Oct 27, 2015 12:09 pm

I think I saw one from him. will ask him.

Pete

Post Reply