Tell me what you think, another "not running right" question.

So here goes. I just put back together my 93 after several days of maintenance. I cleaned and lubricated the throttle and cables, cleaned and checked the gap in the spark plugs, cleaned and lubricated the air filter, changed out the r/r and battery, changed oil and filter, lubricated the chain, and cleaned up some of the scratches in the plastics. After much ado, I hit the start switch and it fired right up on the first try. After a few minutes at idle and fiddling with the setting, it was finally humming along at about 1200-1300 rpm. So, I hit the throttle a few times and then things started going a little funky. The idle wouldn't stay, it kept going high, up to about 4k. Then, after I would dial it down, it would go low and shut off. It was extremely difficult to restart. I was having to use the throttle.
A little background, I had the carbs rebuilt in Oct/Nov last year and bike was running great. In December right before all the snow, it started running rough. It sat over the winter and I would pull it out on the good days and take it for a spin. About 1-2 times a week I would start it up and let it get up to temp. NO, I did not winterize the bike. So, before I took it for the first spin this season, I put some Seafoam in the tank and ran that through it. I've done 2 tanks and am on my 3rd now. It seemed to run a little better, but not great. When the shop rebuilt the carbs, they put new jets in #125 & #128. My manuals (clymer & haynes) both say that for the 93 750F-P I should have #130's. I notice a small popping sound coming from the exhaust when idle and low rpm's. I also notice that there is a gas smell coming from the exhaust almost like I'm running rich.
So this is what I'm thinking. I believe that I at least need a carb sync. I may possibly need the carbs cleaned and check the jets. My problem is wouldn't changing the jets back to #130's make it run more rich? I have a K&N air filter and a yoshi slip on. I'm not sure what to do next. Any and all comments and questions would be greatly appreciated.

Adam

 

I'd begin by replacing the spark plugs. With all your 'cold' season starting and running it's possible one is fouled.

Make sure any vacuum lines are plugged in and that your carbs are pushed all the way into the boots.

Wonder why the shop altered the stock jetting? Do you have a jet kit installed? If so, sometimes they cause more problems than they solve. You may want to quiz the shop that did work on their reasoning. The main jets really don't come 'into play' until throttle is half open or more. I'd be more concerned with the slow jets and slide needles. It's also possible you could have some issue with float valve height adjustment, or needle and seat.

 

Sounds to me like you have an air leak.

Rollin

 

Dizzy - plugs are fine. I pulled them out, cleaned them and checked gap. As soon as I get a little time, I'm going to check vacuum lines and carbs. Hopefully it'll be this weekend. I'm not sure why my local shop changed the jets. They were #132 and I complained that it was running a little rich. They also mentioned that this was a 94 and not a 93. I told them it's a 93 by looking at the vin# and by DMV records. Looking up the jets in the haynes & clymer manuals, they both say that for a 94 the jets are 125/128 and for a 93 should be 130. They may have gotten it confused. That in itself might be part of my problem. I didn't realize it until just recently when I checked over all the paperwork from the shop. Didn't look too hard when I picked it up, was too excited. Thanks for your input.

 

Rollin - I posted on the other forum as well and someone there mentioned the same thing. I'm gonna try and check carbs this weekend. Thanks.

 

Got it, will check those things. Keep the comments coming.

 

My first instinct is to say air leak, because of the idle fluctuation...but having to hold the throttle open to restart is consistent with 'rich' condition. So I'm not sure what's going on.

Try opening the enrichener slightly at idle and see if it helps. If so, it's definitely a lean condition, as in 'air leak' , or jet cloggage. If it doesn't, there's probably something else going on.

You say the spark plugs are fine...that may be. I'm not necessarily reassured by the fact you just had them out to clean and gap. Are you sure you have all four cylinders firing?

 

So, I decided to take another look at things. I checked the spark plugs, they were all getting spark. I took off the air filter and looked into each carb. I noticed that there was some pooling of fuel in #1. I opened the throttle and it dumped on to the valves and when I closed the throttle it pooled up again. I decided to try and clear the cylinders first. After no success (and still not starting or very hard to start) I decided to delve into the carbs for the first time ever. I pulled them off and followed the haynes / clymer manuals to the letter. I found a couple of things. 1) There was some black looking soot, dirt, carbon stuff in the fuel that came out when I turned the carbs upside down. 2) When the shop that I paid a boat load of money to to rebuild the carbs did that, they put it to 1994 spec's (except the float level). Upon double checking the vin #'s for the engine and frame, I indeed do have an actual 1993. 1994 spec's are #125/#128 main jets and #40 pilot and 1993 spec's are #130 main's and #38 pilots. I can't figure out where the black stuff came from. I may have gotten a bad batch of gas. I can't see anything floating through the semi-clear fuel line that I have.

So, here's my plan. I'm going to replace the jets and set it back to 1993 spec's. In the process I'm going to clean all parts. I DO NOT plan on taking off the pilot screws. I also plan on draining the gas from the tank and replacing it with new.

Please let me know if this is a solid plan. Any and all comments welcome.

Adam

 

Make sure your float bowl height is the same for all carbs and make sure the floats are not damaged and still actually float...no leak that would cause them to sink and fill with gas...also check the vacuum piston for leaks

 

There doesn't appear to be anything wrong with the floats or the needles. They appear to be working just fine. The floats do actually float and don't have any liquid inside. Like I said before there was some black sooty (gritty) stuff in the gas that I dumped out. That could be the cause of my problems.

 

What about the thing (forget what its called) holding the float sometimes they get jammed...ensure its working properly without kinking...seriously.

I would take everything apart and clean with carb cleaner and compressed air all jets , pistons, needles just to be able to eliminate the carb completely...

You want to check for leakes at the manifold or intake as well...sorry I know its exhausting sometimes to nail down the exact issue...just pace yourself and be methodical

carbs are not that hard to do...really...if I can anyone can

 

No problem, thanks for all the advice. Just another question, would it be a problem sticking the jets back in? I mean, should I put it back to 1993 version, vice having it at 1994 settings?

 

no not a problem at all...i assume you are referring to the main jet, or all jets... you can remove the jets very easily with a little care and a socket or wrench, or screwdriver once you have the bottom cover of the carbs off..

I would recommend going stock and to the proper year...i am a firm believer in oem for my bikes and my cars...I have never had any great success with any performance mods and don't believe that anyone can match Honda and 50, 000 of their engineers with a 50 employee company....sorry to the naysayers...

let me know what you want to do and I'll tell you how to remove each jet, etc..and of course lots of knowledgeable folks here.you can also go to VFR Discussion and download the factory manual as well as the Common service manual and this should help if you don't have it already.

If you cant find it I may be able to send them to you using a peer networking app like Pagoo, etc...

regards and hope you get your issue solved promptly.

 

davey - thanks for the posts. I planned on replacing the main and slow jets. I wasn't going to replace the needle jet. I figured that there was just a piece of dirt hanging out in there and that is what was causing all of my problems. I am also going to replace the exhaust boots to the carbs. Taking another look at those, they are a little brittle and hard. There looks like there is alot of wear in them also. Got another question though, how do I lean out the mixture if I needed to?

Thanks again.

Adam

 

I was to cheap to do the exhaust boots but its a great idea...there is a mixture screw on the side of the carb that will do the trick...I am looking for a pic of it....right now...

 

Sorry cant find anything adequate...you can lean out by adjusting the height of the carb needle...I did it by switching back to the stock needles and jets from the dynojet kit..

hope this helps

regards