Author Topic: Got my bike back from the shop (Read 5064 times)

TMNT · « **on:** May 30, 2012, 06:25:09 PM »

They tuned the carbs or so it seems. It idles alright. The guy said it was cold blooded and it doesn't smooth out once at riding temp. I road maybe 10 miles or so through some neighborhoods and down a few of the main streets around here. There seems to be a bog in 1st and 2nd. It bogs even when throttle is applied, then all of a sudden it seems to have plenty of perfect power. It almost feels like a older 2 stroke bikes power band to me. Any suggestions before I ask the guy at the shop? It doesn't always do this. Could it have something to do with it basically having a straight pipe as the cores are rot out of the pipes? It does pop a little. Back pressure issue? I cant look at it till the weekend as work has been slammed. Any suggestions? Thank you ahead of time.

1978 cb750f

TMNT · « **Reply #1 on:** May 30, 2012, 06:28:03 PM »

Its ugly as sin but it runs now....just in time for the transmission in my truck to go out...

harisuluv · « **Reply #2 on:** May 30, 2012, 06:37:28 PM »

A lot of these local shop guys aren't as familiar with these older bikes. Not saying that is the case with your guy.

Assuming everything else in order as far as points, valves, etc. etc., and you are suspecting the carbs. What kind of air setup do you have? Did he do any jet changes? If it is a problem with the carbs it could be a multitude of different issues. Needle clip position, float height, jet size, synchronization, etc.

Right away though a lack of immediate throttle response is characteristic of an improperly functioning accelerator pump/assembly. A lot of these guys will just dip carbs in carb cleaner and when they take them out they are "clean." Those little accelerator nozzles are incredibly tiny and difficult to access and therefore are either overlooked or ignored. Hope that helps, perhaps a little overview with your shop guy will point you in the right direction as he is most knowledgeable about your particular setup. Good luck, nice bike!

Tews19 · « **Reply #3 on:** May 30, 2012, 06:47:50 PM »

It just occurred to me. Ask the shop what jets where in there, needle setting they used, float level. I used a shop when I got my first CB last summer. The shop took pics of the carbs for me. I didn't ask him to.

Is the popping on decel or accel?

Decel means its running lean. Cleaning carbs is actually really easy. I wish I would have listened to the members here who advised me to dig into them and they will guide me. A year later, I decided I was done wasting money on shops and it is time I do it myself. My bike runs better then it did the day it left the shop. How clean is your tank? Clean carbs can get messed up with dirt and rust inside the tank.

If you can, invest in new plugs right away. 2 bucks each.. Ride around for a bit then remove and take pics of them. plenty of peeps here can tell you if its running lean or rich by the plug condition. I would contact the shop and tell them it is running liek poop. Good shops back up their work.
If its possible post a pic of it running cold and when its warmed up, running well in your opinion. Again, lots of peeps here can tell a lot from a video.

flybox1 · « **Reply #4 on:** May 30, 2012, 07:29:21 PM »

Quote from: TMNT on May 30, 2012, 06:25:09 PM

They tuned the carbs or so it seems. It idles alright. The guy said it was cold blooded and it doesn't smooth out once at riding temp. I road maybe 10 miles or so through some neighborhoods and down a few of the main streets around here. There seems to be a bog in 1st and 2nd. It bogs even when throttle is applied,......

WTF?!?!

did they do anything besides take your money and spray some carb cleaner in there?
if it doesn't run right, ask for your money back and do it yourself.
spend less than $150 on rebuild kits and on a dial vacuum gauge.
you'll be done in a weekend with help from the forum, your bike will run better, and you'll be that much smarter, too.

TMNT · « **Reply #5 on:** May 31, 2012, 07:08:11 AM »

I can only go to the shop on Saturday but When I take off in first even at half throttle it sounds boggy and doesn't really move fast as it should...then all of a sudden the power will kick it and it goes. I have only got it to about 40MPH but it does this in 2nd and sometimes 3rd gear. It seems really boggy till the "power band" (for lack of a better word" kicks in. I will ask (unless he seems this first) which needle size is in them right now. I have very little time to work on it between school and work and living in a apartment. Any suggestions on what is going on? It also is hard to start without the choke at least half out.

TMNT · « **Reply #6 on:** May 31, 2012, 07:10:34 AM »

Also, I am not sure if the shop did a test ride as it is pretty much illegal to ride right now. 1998 plates/turn signal lenses are gone (need new ones)...horn isn't working.

LesterPiglet · « **Reply #7 on:** May 31, 2012, 07:14:43 AM »

You rode 10 miles and managed 40MPH? I'd be back at the shop pronto!

iron_worker · « **Reply #8 on:** May 31, 2012, 07:16:46 AM »

Sounds like they just either sprayed some sh!t up into the carbs and called it good or dunked them in something and called it good.

I would guess that you have plugged idle jets, your accelerator pump isn't working correctly, and you may be set up with stock jets when it in fact should be jetted up with the mods you have.

IW

flybox1 · « **Reply #9 on:** May 31, 2012, 07:18:13 AM »

this gets me The guy said it was cold blooded and it doesn't smooth out once at riding temp. cold start, ok, i will believe that. but isht running when warm? no. he did you wrong

timing/advance needs to be set.
valve lash needs to be dialed in.
carbs need to be thoroughly cleaned, paying particular attention to the pilot/main jets, and emulsion tubes.
they need to be spotless and clear of blockages. all varnish needs to be cleaned out of the carb bowls and passages. gas tank and fuel lines need to be drained of all old gas, and before fresh gas is put in, the tank need to cleaned of all debris and rust.
fully charged battery. new air filter. start.

vames · « **Reply #10 on:** May 31, 2012, 07:40:21 AM »

If most of us paid shops to do necessary work each time our bike needed something done, we'd be into most of them for tens of thousands. And that's assuming shops gets things right the first time (which they often don't) and don't charge us twice or three times more just to keep trying to fix something. Not to mention that professional mechanics are not necessarily magic -- they troubleshoot and get led down blind alleys and try indiscriminate fixes that cost money and don't help the bike just like the rest of it. Many are lazy and won't clean a carb with the same love and care that we'd clean our own carbs with.

The point: This vintage bike thing is a hobby as well as a sport and a practical transportation solution. Hobbies take time. Unless you are very rich, I don't think it's economically viable to own a 40-year-old bike and not spend a requisite amount of time wrenching.

You can keep bringing it back to the same mechanic over and over again until winter sets in and riding season is over. There's no guarantee that he's going to make your bike run well and every guarantee that he's going to keep finding things to charge you for (at highly inflated parts prices and time spent fumbling).

phil71 · « **Reply #11 on:** May 31, 2012, 07:48:34 AM »

To add to what Vames said, don't go back angry.. not fixing it thoroughly is not necessarily a malicious act. We don't know what you paid him, or what your instructions were. If you said "here's my bike, get it running'.. he did that, I suppose.
You're here now.. the vast knowledge and experience of many talented hobbyists is now at your disposal..

Tugboat · « **Reply #12 on:** May 31, 2012, 08:19:30 AM »

Quote from: vames on May 31, 2012, 07:40:21 AM

If most of us paid shops to do necessary work each time our bike needed something done, we'd be into most of them for tens of thousands. And that's assuming shops gets things right the first time (which they often don't) and don't charge us twice or three times more just to keep trying to fix something. Not to mention that professional mechanics are not necessarily magic -- they troubleshoot and get led down blind alleys and try indiscriminate fixes that cost money and don't help the bike just like the rest of it. Many are lazy and won't clean a carb with the same love and care that we'd clean our own carbs with.

The point: This vintage bike thing is a hobby as well as a sport and a practical transportation solution. Hobbies take time. Unless you are very rich, I don't think it's economically viable to own a 40-year-old bike and not spend a requisite amount of time wrenching.

You can keep bringing it back to the same mechanic over and over again until winter sets in and riding season is over. There's no guarantee that he's going to make your bike run well and every guarantee that he's going to keep finding things to charge you for (at highly inflated parts prices and time spent fumbling).

+1 on all that!! Sounds like idle jets and/or accel pump to me... also sounds like there was no "tuning" going on at all!!

mono · « **Reply #13 on:** May 31, 2012, 08:34:54 AM »

+1 on what flybox said, and +1 on everyone else's suggestion to do it yourself. i was really intimidated by the thought of cleaning my carbs, but once i got through cleaning/rebuilding the 1st one, i was laughing at myself for thinking it was hard.

there are zillions of threads on cleaning/rebuilding/syncing carbs on this forum, and your service manual should also offer a good step-by-step.

I'd start by gapping the points and adjusting the timing, then if it's still wonky, tackle the carbs. for me, a good cleaning and bench sync got my bike running way better. also replace all the o-rings on the intake. vacuum leaks are the enemy!

bollingball · « **Reply #14 on:** May 31, 2012, 08:53:20 AM »

This has been on going for a year and a half is this still the same shop and guy working on it ? Project Shop / 400$ and a title...ok!
« on: January 29, 2011, 06:46:48 pm »
1978 cb750SS 19K miles on the Odometer...complete save for the side panels. Its going to be a fix and ride type of thing...for now. Last owner says the carbs are clogged...he is my mechanic and pretty straight forward. Things I need first.
battery
brake cable/s
throttle cable
petcock
tank cleaned and sealed
It has been sitting out in the weather for a while so all the cables are all stuck and/or sticky.
I think I will try some seafoam in the carbs to try and cheap my way into atleast getting it running.
after running
tires
hopefully the carbs are my only problem as it does feel like it has nice compression when I kick it over.

We will see

Duke McDukiedook · « **Reply #15 on:** May 31, 2012, 09:45:06 AM »

Like everyone else has said if you have decent spark and timing is correct then your carbs were not sufficiently cleaned.
The only real way to know if it was done right is if you do it yourself. You can dooo iiiiiiiit!

TMNT · « **Reply #16 on:** May 31, 2012, 03:31:52 PM »

Alright.. here is the story. I bought the bike at a time in my life when I was in a heavy transition (that continues). This year has been absolutely crazy for me. Mainly drug addiction (8 months clean) and heartbreak. You older guys remember the 20s and those heartbreaks where you find a girl you believe to be "the one" and turns out to be not the one in drastic and dramatic fashion? I live in a apartment. the bike has been sitting at my parents house mostly. The main problem I have had is trying to save cash for it...and making bad decisions once that cash is had (like allowing a scumming cousin wrench on it). The shop I took it to was suppose to just "tune" the carbs. I was told the floats were not level. I got these carbs from a guy one here who rebuilt them. I trust that they are in semi working order and bench synced. I am living paycheck to paycheck right now so money is very tight as I am sure you all understand. As of right now I plan on just riding my bicycle to work as my trucks transmission went out 2 weeks ago for the second time. I am just going to do this #$%* right with this help of this forum. Another thing is time. I am 27 years old right now and started college for the first time last year and as a 27 year old who feel time is of the essence in school my classes are loaded even in the summer...along with working 50 hours a week. The good thing about this new job is I have weekends off. So Saturday I plan on re-reading this post and start from there. Sorry if there's a bit of a sob story in there (I could definitely make it way sobbier)..haha

I will update this Saturday. thanks again

750K · « **Reply #17 on:** May 31, 2012, 03:51:17 PM »

I had the same #$%* happen this winter after a motor rebuild, carbs were rebuilt as well. Mechanic said it doesn't like cold starts and runs rough till it warms up, turned out to need the points adjusted as well as a carb sync and mixture adjusted. It was lean as well as not even close to being in sync, I went back and confronted the owner and tech. They offered to make it right, I just did it myself. In my case the carbs were pulled apart and cleaned with all new gaskets and orings put in, the tech didn't even sync it...

It's not like I don't know how to work on my bike, I didn't have the time to do it. Gutting my basement was taking all my spare time not to mention working full time, in the end I made the time and did it myself. Runs like a top now, starts up quick cold and runs smooth. Pulls hard in gear now and does not sound like a twin, sounds like an inline 4 again...

Do it yourself, and know it was done right.

HondaMan · « **Reply #18 on:** May 31, 2012, 04:00:02 PM »

Perhaps start by checking the adjustment of the idle screws. On the PD carbs, these are on the bottom front of each carb, hard to get to: make sure they are all set to the same number of turns out from all the way in. Don't bottom them hard: they are fragile and easily damaged. Use a SHORT screwdriver to turn them. I think the F3 setting is 1.5 turns out, should be close to that, and all should be the same.

There are teeny, tiny O-rings at the tips of those screws, and I often see these in pieces when I clean those PD carbs. The pieces are hard to get out...once out, it can be tricky to get them back in straight, and the new ones must be soft and supple, or they won't seal right. Some of these PD carbs also have a teeny washer that holds this O-ring in place, but not all of them are like this, so keep an eye out for that tiny piece if you take out the screw(s) !

Personally, I think SOHC4 bikes make great 'rehabilitation' projects...

Tews19 · « **Reply #19 on:** May 31, 2012, 04:39:08 PM »

TMNT, hang in there. Karma has funny ways of playing itself out. I wonder if there is anyone on here who is in riding distance from you who can help. Click on your original post and modify the title. You can change the title that way and may catch someones eye. Remove your points cover and see how the spark is. Can be done in a sec. Also, if you have a seperate spark plug that is good and not being used. Remove each plug wire and plug in spark plug. See if there is spark to each cylinder. Literally can be done in a minute total. You can do this and report back right away. I think you said it has spark to all 4 but doesn't hurt to check again. Also, if you have a spare spark plug, you can leave your spark plugs in the engine when you test each wire...... Go to walgreens and buy a nail file. One that is metal and doesnt have glue/sand.. Swipe them through your points....

PM your info if you want. I will send you brand new points and condensers for your bike. I bought them and with the help of peeps here found out mine are fine. You can have them for free. Points may not be your fix as I am with everyone else when it comes to what could be the issue. But if you do remove your points cover, see one isn't performing right. I will send them to you.

jakecb420 · « **Reply #20 on:** May 31, 2012, 07:52:28 PM »

Quote

PM your info if you want. I will send you brand new points and condensers for your bike. I bought them and with the help of peeps here found out mine are fine. You can have them for free. Points may not be your fix as I am with everyone else when it comes to what could be the issue. But if you do remove your points cover, see one isn't performing right. I will send them to you.

thats just one of the reasons this forum is better than the rest.

dougan · « **Reply #21 on:** June 02, 2012, 07:49:14 PM »

Haven't had much experience with my CB yet, but my moped ran this way for awhile-- bogged down, randomly would 'kick in' with a heavy lurch and it'd be running perfectly fine until it bogged down again. Carb was set too rich, and adjusting fixed it. Also had an outboard that did this, and it was the stator, which was an expensive fix i had a mechanic do. This info probably does nothing for you, but you get what you pay for.

If it were me, I'd try to take the carbs apart and tinker with it yourself. Even if you're not quite confident about it. If you can find a video or forum thread on how to mess w/ your specific bike's carbs, you are probably more informed than your mechanic was. If you can't get it back together then take it back to the shop and ask if they can put it back together for you. Explain (politely) that they didn't do it right the first time, so you wanted to take a look yourself before paying to get it looked at again-- at that point, them putting it back together for you is the least they could do. I'd think/hope any half-decent shop would do this for you.

Xnavylfr · « **Reply #22 on:** June 03, 2012, 04:52:12 AM »

One thing I have noticed ,NO one has mentioned to check your gas tank and fuel flow for crud from the tank. If these OLD 750s sit long, rust will appear in the tank and start to clog your petcock then your carbs. The petcock has a small bowl on it , inside is a filter screen. Remove the bowl and see if it's rusty looking inside. If there is rust then if you clean the carbs, the first time you start it they will plug again.

Xnavylfr(CHUCK)

lucky · « **Reply #23 on:** June 03, 2012, 01:23:19 PM »

Quote from: TMNT on May 30, 2012, 06:25:09 PM

They tuned the carbs or so it seems. It idles alright. The guy said it was cold blooded and it doesn't smooth out once at riding temp. I road maybe 10 miles or so through some neighborhoods and down a few of the main streets around here. There seems to be a bog in 1st and 2nd. It bogs even when throttle is applied, then all of a sudden it seems to have plenty of perfect power. It almost feels like a older 2 stroke bikes power band to me. Any suggestions before I ask the guy at the shop? It doesn't always do this. Could it have something to do with it basically having a straight pipe as the cores are rot out of the pipes? It does pop a little. Back pressure issue? I cant look at it till the weekend as work has been slammed. Any suggestions? Thank you ahead of time.

1978 cb750f

Same old story.
The shops just do not know enough to work on these bikes.

With the bike OFF look into the intakes with a bright flashlight and turn the throttle and see if the spray nozzles are even working. I bet they are not.
If it has the stock idle jet with non stock exhaust there is no way it will idle right even with the stock airbox.

lostmykeys · « **Reply #24 on:** June 03, 2012, 08:01:44 PM »

TMNT,
I think you should look at the threads I have started especially reguarding the accelerator pump and just read through them for a while.
I have the same bike that I just aquired in the last 6 weeks and I still have a way to go with it but its night and day from where it was when I took it on trade.

News:

Author Topic: Got my bike back from the shop (Read 5064 times)

bollingball