Replacement of Intake Boots

I have a completely beater bike, 1990 Yamaha FZR600, this bike has been over-abused and neglected from proper maintenance. And I ended up with it for lack of better judgement and needed it before I went back to college. Anyway, I'm not mechanically inclined, so I took it to this mechanic shop run by one guy, long story short, he mooched a lot of money out of me, and wants more. He says my bike needs all intake boot replacements. And the parts aren't too expensive, but his labor charge is.
Problems:

When I start up the bike (it doesn't have a choke, so conditions need to be warm) I need to give it throttle as I'm hitting the starter button.

If I leave the bike on idle for a while, the engine shuts off. So I have rev it like crazy.

And the most dangerous part, when I brake while riding to slow it to idle speed or come to a complete stop, instead of going back to idle, the engine shuts off.

Symptoms:

When I am revving it above 8K and the bike is immobile or just going steady and then increasing throttle above 20 mph, the bike misfire like a loud thump or fart, and I saw a little spark and smoke come out of the exhaust.

The guy said he cleaned out the carbs (the carbs was already cleaned) and replaced the spark plugs (the previous spark plugs were new anyway), so it couldn't be the carbs malfunctioning.

Anyway, I ordered the manual from ebay. So has anyone ever had to replace the intake boots? The mechanic claims there is an intake leak preventing proper airflow to the carbs.

Other problems:

Rear brake needs rebuilding, change tyres, change engine oil, etc. But those can wait as long as I can get the bike to up and running first.

Advice would be appreciated, thanks.

Pros: The motor is strong, only has a 13.5K mileage for a bike this old. And it has Vance & Hines full exhaust and probably jet kit inside, even though I haven't looked inside yet.

I'd change the oil before much else. If the oil is like tar, the bike won't run well no matter what you do to it. It sounds silly but make sure the air filter isn't gobbed up. Filters aren't very expensive, and tend to be forgotten in terms of motor effectiveness. As for intake boots, I'm by no means an expert, but I haven't heard this term before. Your engine isn't very different from mine... we share an air filter, as a matter of fact, so I will go through my repair manual and see what they are.

Well he called them intake "boots", but as he explained, it's the joint between 4 carbs, there are 4 of these boots I guess. Basically the intake is leaking and unable to pump full air flow to the carbs, and hence running the engine. The idle speed is also low because of it I guess. He said in the future, it might do permanent damage to the engine when revving it hard, no one knows when. His words were shady, like : "I can't say anything will happen, and I can't say anything won't happen. Just letting you know. You gotta get it fixed soon."

i think your being scammed. i've never heard of intake boots, but with your carbs exposed i.e no airbox/filter/"boots" the bike should be able to suck as much air as required and go really well. best intake is no filter but shit will end up in your motor. to check this out, soak some pantyhose in oil and use it streched out over your carbs as an air filter.
gotta love high school style mechanics.

might be an exhaust leak stopping the required back pressure at low revs or a timing problem. check all high tension leads for any cracks that may be shorting to the nearest metal.

change all the fluids and brake pads and lube the cables. if its only done low milage and is 14 years old its probably never had lubed cables. use a graphite based product. don't use a WD40 style product as its a degreaser and will feel great for awhile but will strip out any lube quickly. don't mix graphite with a WD40.

good luck. maybe try another mechanic. took me 5 before i found one to trust

Sorry, I know this is a little off subject, but I was reading about Jet Kits from Dynojet, and I noticed the stage 2 and 3 kits recommends a modified airbox. Can I even modify the intake of my F4, it has the ram-air style airbox? I know filters are made for it but what are they talking about? THANKS!

Its my beleif that Z's talking about the intake manifold boots.... IE the rubber transitions that connect the carbs to the engine. If a leak were to happen on one and not the others then that cylinder would run lean (too much air in the fuel/air mixture). The lean cylinder would run hot. The lean cylinder could eventually (possibly) scorch a valve, warp or crack the head, gauling of the piston, scoring of the cylinder...... all these things are other then good.

I'm not going to try and get his quote verbatam but it said something like "low miles for fifteen years, vance and heins and probably a jet kit"

Its my expierence that any time you change the way the engine breathe's(inhale and exhale) that the fuel air mixture needs to be adjusted (re-jet)
Lets say you take off the stock airbox and filter the intake with an oily old pair of panties...... (what an idiot) hehe! Your changing the way the engine breaths... Its much easier for the engine to breathe without the X amount of foam filter that has been replaced by aussies greasy, flow through knickers.

Same is true of the exhaust.... installing a high performance exhaust system -or- removing the baffle -or- even changing from say a 4 into 2 Yamaha exhaust into a 4 into 1 Yamaha exhaust from a different year. (if this example is actually available I dunno.) My point is that if you modify the way the engine exhales, again, if you make it easier to exhale (less back pressure) -or- if you make it harder (more back pressure) THEN THE FUEL AIR MIXTURE SHOULD BE ADJUSTED.

If your planning to do some improvements to your bike....its wise to do all the airbox/intake/filter modifications AND install your improved exhaust system at the same time and then re-jet the carbs and dial them in. Zfan could even rejet to correct for the leaking intake boot as long as it would not change (get more or less of a leak)

I would not ASSUME that the jet kit was done.... I wouldnt open the carbs just to check either..... Rejetting is an educated trial and error procedure. Not for the weak at heart or the first time amature.... Now you'll never become an expert unless you do a few so remember "no guts, no glory" It entails, as I know it to be..... and there is probably new equipment that makes it easier, but. Riding at a spirited rate of speed (safely).. killing the engine in flight, and coasting to a safe stop (without the engine/trans engaged) in neutral. Then you remove and evaluate each spark plug ...... From there you remove and open any carb that requires adjustment, change that jet (either up or down depending on how the sparx read) (expierence will tell if you go just one size or more in either direction) Put the whole mess back together, get back out on your test trax and run it fast again to kill the engine to coast to a safe stop to pull the plugs to read them to descide if you need to take all that stuff back apart to change more jets..........

To me it sounds like an awful alot of Heineken..

I also hear tell of , and I am looking to get one, its a neat spark plug for test purpose. I has a little mica or clear quartz window on it that lets you see the color of the fire inside the cylinder. Again, you evaluate the color and adjust the fuel/air mixture to its optimum ratio... If anybody know where to get it or what its called.....Do Tell!

Well, I'm running out of ink now, so good luck and all that stuff.

I apologise Blayne, I couldn't resist :evillol:
Disclaimer: These opinoins are the ramblings an alcohol contaminated brain. Use this advice at your own risk. All disputes arising out of you utilizing this advice will be settled out of court.

This bike has been raped basically, and that's the best way I can describe it, even the sidestand is gone. The idiot before, whoever, put a jetkit in there and couldn't make it work. So it could be something wrong with jetting as well. I have to wait 10 mins until the bike warms up. Eventually I'll have to put a choke or pull the jetkit out. Fabricgator is right, it's probably intake manifold boots, intake tubes, carb boots, etc.

Gator I could use your expertise if you got free time in the future. And 6 pack, 12 pack whatever you can chug will be on me. :D

hey what 16yr old with a 1976 ford escort 1.6L single carb hasn't flogged his mums knickers to replace the air filter just before going out on a friday night to go cruising with a really loud induction note down the local chick magnet strip only to be blinded (not by the reflection of the sun refracting through a cheap earing (apologies to R1 RIDER) but )by the oversize novelty disco ball hanging by the interior light. oh shit this could go on and on so i'll shut up now

Z, are you SURE there isn't a choke on there already? I know my Yammy has a choke that sits RIGHT ON the motor... I didn't think mine had one until I found this lil black knob on the left side under the gas tank by my knee. Make CERTAIN that yours isn't hiding in there too. I can't find my repair manual... it seems to have disappered temporarily, but I will see if I can help you in anyway since our bikes are fairly close in vintage.