backfires and crazieness

[Guest]

im confused

i have fixed a short in a plug wire boot and now the bike will limp along at idle for 10 seconds and then backfire and rev up to 3grand. do i have a coil problem or should i look into a carb rebuild?

[jesustheplumber]

(continued)

perhaps i should give a little more information to add context.

i have had this bike for several months and have yet to see it run right. i know the carbs were messed with but im not sure how. im 90% sure my problem here is electrical because before replacing the boots on my plug wires i could pull the plug wire off the spark plug and the engine would rev stupid high and when i snapped it back on it would die back down to normal.

perhaps a little more context to the overall condition of this bike:

1)a previous owner thought it would be cool to hack the exhaust off and weld on cherry bombs

2) there are obvious signs of.... ghetto rigging (rtv on intake sides of carbs)

3)i have no clue of the maintenance history of the bike (valve shimming, oil changes, etc...)


I'm starting to feel like a shotgun approach (replace everything) is necessary but i realize my wallet is also on that end of the shotgun.

any help will... well.. help.
,Thomas

[keman]

Welcome to the site (and the addiction to motorcycle masochism)

The most common reason for crazy revving is air leaks on the intake side. Especially the o rings between the Carb manifolds and the head (also the most pain to replace) :-) before looking at the electrical issues, make sure that everything on the intake side is sealed correctly (no RTV ).

There is a great tutorial on Bikecliffs site, (linked in my sig) :-) for rebuilding your carbs. Every GS veteran on this site will tell you... REBUILD YOUR CARBS. Follow the tutorial, don't take ANY shortcuts. Its really not hard if you follow the tutorial step by step. You will find a complete set of carb o rings at cycleorings.com, (don't forget to get the manifold o rings while you are at cycleorings. .. Then get bowl gaskets at Z1enterpriszes.com (YOU DO NOT NEED A REBUILD KIT, most Carb kits sold online are full of crap parts)

Next, go through your wire harness, clean or replace all of the connectors. Check for hard or brittle wires and replace any wires that need it. Pay special attention to your ground wires and ground connections.

[jesustheplumber]

thats what i was fearing. i at least wanted to ride it around a few more times before disassembling it... but i have started a list. and i have read and re-read the tutorial by paul musser for rebuilding the vm style carbs. and i have read and re-read the rebuild section in my clymer manual.

ill do a full inspection and make a final parts list tomorrow but i guess i can try a rough list

o-ring kit for carbs (cycle orings)
gaskets for carbs (z1)
pod intakes? (will need to re-jet)((never done that before))
intake o-rings (cycle orings)
ultra sonic cleaner and simple green(harbour frieght and DG)
new intake boots(where to get)
motivation

did i miss anything?

[jesustheplumber]

Welcome to the site (and the addiction to motorcycle masochism)

masochism, eh? with what this bike looks to have been through, i cant help but wonder which side is getting abused?

[BassCliff]

Greetings and Salutations!!

Hi Mr. jesustheplumber,

I've been away so I apologize for being late with your "mega-welcome".

On a bike with an unknown history, it's probably best if you go through every system to make sure everything necessary gets cleaned, repaired, replaced, adjusted, etc. Start with clean carbs and then go on down the maintenance lists linked below. You'll find lots of tutorials and information on my little website.

Let me dump a TON of information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...



Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[TheCafeKid]

A good start would be to let us know which model you have

And yes if the exhaust system isn't stock, and/or the intake system isn't stock, a re-jet will be necessary. As you've already seen, starting with clean carbs is absolutely required. 9 times out of 10 they've not been properly cleaned and rebuilt in lord knows how long. The orings become trash, this ruining the sealing properties they're required to have. It's a crucial step, and many people simply disregard this and think that a blast of carb spray is going to cut it. It won't, and months later after refusing to do a few days (really a few hours of actual work but it's a lot of hurry up and wait ) worth of work and some simple instruction following thanks to the excellent tutorials put together by Ness and others, they give up and sell the thing...

That doesn't make us too sad cause usually one of us will pick it up on the cheap and have it kicking ass in a couple weeks Don't be that guy!! See it through.

As to a rejet, it can either be easy or not so much depending on your model and your level of experience with carbs.
If a DynoJet kit is available for your model, that's the easy and effective and quick way to do it. Yeah, it's gonna cost about another $120, but in a couple hours (with fresh clean rebuilt carbs or course) you're gonna be amazed how much better it runs if you follow the detailed installation instructions.
If you've an older model (pre 1980) with mechanical carbs, it's a bit more involved but usually only a new set or two of main jet sizes will be required along with some educated guesses to get you in the ball park from the guys here, and some other adjustments.

There are no short cuts unfortunately. Generally you're going to have 15-20 years worth of neglect to rectify. Such is part of owning an older bike. Many pick up an old GS and think they're going to ride off into the sunset for cheap only to find that if they see it through they're easily another $500-$1000 into it over the initial purchase price. BUT once you get all of that neglect worked out, you'll not only have a great running bike that will continue to run for many many years but the knowledge required to keep it running that way.

And that's when the sickness really sets in. You feel empowered by the fact you're riding something you rescued from motorcycle hell..but now you simply have to do another one!!! And before you know it, youve got 4 GSes in the garage, and you bought, fixed up and sold to good homes ten more!
And it still isn't enough.....

Welcome to the GSR

[Steve]

pod intakes?

I would really suggest getting the bike to run properly in STOCK condition, then make changes, knowing your starting point.

As far as your priorities, riding the bike should be rather far down on the list. Get EVERYTHING working properly, then carefully go for a ride. Coaxing the engine to life just to go for a ride and find out the brakes don't work is quite foolish, so get it ALL done.

And that's when the sickness really sets in. You feel empowered by the fact you're riding something you rescued from motorcycle hell..but now you simply have to do another one!!! And before you know it, youve got 4 GSes in the garage, and you bought, fixed up and sold to good homes ten more!

We only have FIVE of them in our garage.
and three other bikes, too.

.

[DanTheMan]

A good start would be to let us know which model you have



And that's when the sickness really sets in. You feel empowered by the fact you're riding something you rescued from motorcycle hell..but now you simply have to do another one!!! And before you know it, you've got 4 GSes in the garage, and you bought, fixed up and sold to good homes ten more!
And it still isn't enough.....

Welcome to the GSR

Hey, Josh! Stop it! I resemble that remark, I've got two runners, one parts bike, and one waiting on a title to restore. My Jeep (in the midst of a re-wiring project) is in MY garage, my bikes are in the attached garage (my WIFE'S garage) It sure is nice having a co-dependent/enabler in the house!
Welcome Aboard, read all the good stuff, you'll have a safe, working bike soon!

[AJ]

First, I agree with many of the suggestions above.

Speaking from recent experience with a bike that had a grossly oversized exhaust and was not properly jetted, backfiring is a common symptom.

Are you running without air filters?

That plus cherry bombs for exhaust will mean you'll need much bigger main jets. You might get it to idle ok, but she won't rev, and if you hold the revs up to whatever peak RPM she *will* go to, then she's gonna spit and complain and backfire. The mixture is too lean, you get incomplete burning of the fuel which then fires inside the exhaust pipe.

First, hook up your filters. These carbs don't do well without any filter.

You can probably add pod filters and rejet the carbs to get it to run "ok" with those cherry bombs, but I will tell you that those straight-through, large diameter glasspacks give wayyyy too little backpressure to ever get the bike to run well. You will sacrifice torque and all your power on the low RPM end and only get a big rush at redline. You need backpressure.

As a test, figure out some way to restrict your exhaust pipes to a hole no bigger than 3/4" in diameter if running 2 pipes, or 1 to 1.5" in diameter. You can probably punch a hole in the bottom of a soup can, cut a slot in the open end, and use a hose clamp to get it attached to the end of the pipe. If you need to, use a little household fiberglass insulation to make a gasket to seal the can to the exhaust pipe. Now see if she will rev higher and if the spitting/backfiring gets better. If it does, you have a better starting point to work with.

For a cheap set of pipes, look at Craigslist for a set of Harley Sportster mufflers. Guys rip those off brand new bikes and they sell for about $50 in beautiful condition. The Sporty mufflers actually work pretty well with a nice tone and I have seen them on many classic bikes.

[MisterCinders]

thats what i was fearing. i at least wanted to ride it around a few more times before disassembling it... but i have started a list. and i have read and re-read the tutorial by paul musser for rebuilding the vm style carbs. and i have read and re-read the rebuild section in my clymer manual.

ill do a full inspection and make a final parts list tomorrow but i guess i can try a rough list

o-ring kit for carbs (cycle orings)
gaskets for carbs (z1)
pod intakes? (will need to re-jet)((never done that before))
intake o-rings (cycle orings)
ultra sonic cleaner and simple green(harbour frieght and DG)
new intake boots(where to get)
motivation

did i miss anything?

You should get the tools and shims to check and adjust your valves. From your sig, I assume this is the 77 GS750. You can pick up the "special tool" for about $15 or try the zip-tie method on BassCliff's site. Zip-ties never worked for me, but I have never had any problems with the special tool. YMMV.

For shims, the best thing to do is check your clearances first. You may need only one or two shims, so buying a full set is way more $$$$ than you need. There also is a shim club on the forums. Before you do the check, see if your local bike shop or dealer has any shims at hand. Picking up one or two of those for $5 a go will allow you to shuffle your current shims around to bring them into spec, if possible. Without at least one spare, you won't be able to turn the cams for certain swaps. Never turn the cams without a shim in place.

HTH

[jesustheplumber]

ok,

basscliff
thanks for the welcome! I've yet to meet anyone on this forum who didn't make me feel welcome, and I will certainly consider supporting this site when this bike is running. the information on this site has already proved to be more than worth my support.

thecafekid
first off im not far from dayton so if you ever want to stop by PM me and ill be more than willing to show you this bike. and goodness knows i could use some help with the thing. it is the '77 750 b in the sig. i dont know if the wallet will allow 4 gs' but i would if i could

steve
i wouldnt mind putting the bike back stock for a while to get a baseline to start from like you say, but since this is my first bike, i dont want to spend to much money until i get a feel for what i like. i suppose i can put off pods and deal with a stock or close to stock exhaust. those cherry bombs look idiotic anyway. suprisingly they don't sound bad though. any suggestions for a good "close to stock" exhaust for cheap? i dont care if its just a beat up set of old pipes. ill weld the holes shut

ajay
sportster mufflers? how close will those put me to the stock mufflers?

mistercinders
i started pondering the valve adjustments and an oil change after my last post. i suppose it would be easy enough to do that while letting the carbs soak. but ill have to do more research of the process and perhaps then ill know wether its zip ties or tools. though, zip ties have never failed me in my past riggings.

[TheCafeKid]

Oh you're in Franklin?? Haha I work in Springboro and actually live in Miamisburg. Heck you should come by, or vice verse I would be happy to lend a hand and show you "the ropes" if ya want...
By the way I may have a set of decent enough stock mufflers to part with if you don't wanna go the harley pipe route. I also have a fair collection of 77-79 750 parts and such too..

[jesustheplumber]

thecafekid

i would love to get together on this bike, but youll have to give me a little time since we just went through a massive spring cleaning on the garage and im still getting my space to work put back together.

and if you have some old exhaust laying around ill definetly be interested in it. and if i ever need some parts ill holler at ya!

[jesustheplumber]

ok so i have made a list of stuff to order/ get and some quick prices. i still dont know where to get the boots for the airbox.

16 mm stainless fasteners. cycle orings - $6.90
vm o-ring kit - cycle o-rings - $18.85
32mm intake o-rings - cycle o-rings - $3.30
boots for the airbox -?-?
ultra sonic cleaner - harbor frieght - $75
simple green - dollar general - couple dollars
carb sync adjustment tool - z1 - $15.99

and then a few other ideas

get stock exhaust (exhaust gasket?)
rotella diesel oil
shim the vaves
check the coil packs

any thoughts guys?