Re-jetting GS450S w/ Mac 2-1 Exhaust

[Anonymous]

Hello,
I just ordered a Mac 2 into 1 exhaust system for my '80 Suzuki GS450S. I know I am going to need to re-jet the carbs after I install the exhaust system. My question is what size jets were factory installed and what size jets would you reccomend going with, I live in the panhandle of Texas? Also the carbs appear to have a factory plugin them where the jets or air screw should be. Am I going to need to drill that out to sync my carbs? I have tried syncing them before but I am not finding any adjustment screws on the carbs. How to I adjust the timing it appears to be missing at higher RPMs? The repair manuel I have covers adjustment of breaker points but mine doesn't have breaker points it has what looks to be magnetic pick-ups.

Thanks,
Jay

[bgmart450]

I'd put them on and see how it runs. From what I have heard the Mac is a direct replacement for the 2-2. I think it might run ok with the stock jetting.

Stock jetting specs can be found ..here..

If I am not mistaken the sync screw is on the linkage between the carbs. Actually it is, so says Haynes. Its a small flat headed screw.

You'll have to drill the caps to get to the air mixture screws (not for syncing), but removing the screws will require new orings for them. That part is not listed anywhere, but I am sure you can find a replacement in many places. Unless you are going to dip the carb bodies you could likely leave that alone.

Sounds like you could use a new shop manual The timing is checked under the right hand cover (there's a small round cover you have to remove, not all of it). There's a ATU (automatic timing unit) plate there thats checked with a strobe light. I'd put more, but short on time. If you can't find more and I can gain access to a scanner I can scan those pages for you.

Nice to see another 450S in the states (and an '80 no less).

[Anonymous]

I have a shop manuel it is a Clymer. Under timing it says no adjustment necessary if it doesn't have the breaker points. Which I disagree with. Looks like I need to get my hands on a better manuel. If it isn't too much trouble could you scan those pages on timing and email them to me? jayrbaker@gmail.com.

I love my 450S, the first bike I jave owned, but it is hard finding parts for it at times. I bought it off a person I use to work with for $600 in June '04. After buying it I had to put a new stator in it, I was able to find one at a bike junk yard here in town. Then, I was able to ride it for about 2 months when a valve broke and tore the left cylinder to pieces. Looked into getting it repaired/repairing it myself and it was a bit expensive for my budget at the time. Bought a used 450 engine off ebay for $50 bucks plus shipping (which was about $200). During the down time I repainted the body and put new brake pads on (front and back). Had to swap out clutches between the two engines and put some new plugs in; I finally got it going again last week. I use the bike for commuting from home to college, its about a 20 mile commute one way. So far it is running pretty good, except for the high speed misses and needing a new chain. The mileage is about 40mpg. Going to check the valve clearances this week hopefully. The seat needs to be recovered, it has a few tears in it, and I need to put new pin stripes on it. I am also keeping my eye out for a '52, '49, or '95 Triumph Thunderbird and an '80's GS750E. When I find one I can afford and get it going I am going to have the frame powder coated, engine polished, all crome polished, etc. get it like brand new again.

[gspaul]

450s american spec used to get up to 60 mpg( my 650 gets 50 and I tend to ride flat out)
Yes do your valves,check you air filter.
If it looks like your timeing plate has not moved it's prob ok .
,but you can check the timeing any way.
Might need a carb sync , but prob needs a good carb clean out.

[nabrams]

You Clymer manual is correct. Your 1980 GS450S has CDI ignition, NOT points ignition. There is a tiny amount of free-play (after loosening the two mounting screws) in the signal generator plate that really allows no appreciable adjustment. There is a tick mark on the plate that should align with the tick mark on the engine - If that's OK, then you need not adjust anything.
Something that is possible (and happened on my friend's GS450) is that the wiring leading to the signal generator may be frayed/corroded which would affect the firing at higher RPMs (more vibration there).

[Anonymous]

I did a good carb clean out and rebuild this winter. While I was waiting on the engine to arrive. I think my gas mileage could be due to my compression. I am only getting 110psi when I should be getting 130-170psi a Clymers. I am not comfortable doing a ring job myself just yet. My air filter is brand new, I will check the wiring lead and get back to you. Just need some time and some feeler gagues to check the valves. How difficult is it to check the valves? Sounds a little tough to do from the Clymers book. I am a computer "geek", and construction junkie. That has some engine knowledge but not alot.

[bgmart450]

Hey, did you win that motor from WI? LOL I was bidding on that... I was able to get a cyl head from NY (way closer) cheap, so no biggie

I get around 40MPG myself, but I have an open airbox, larger jets, and waaaaaaaaay less restricted exhaust that stock. I need to check the wife's bike for gas milage one of these days.... Hers is bone stock minus the paint.