Hi, all. 1986 fj. Since I got the bike and after rebuilding the carbs, the bike at 1/8 throttle opening it's not running right. If you keep the throttle steady, rpm don't rise and make a pingpong sound, otherwise the bike runs fine. I checked the timing and this is what I found. TDC at crank,exhaust cam cap aligned with the hole but intake cam it's not in center. What do you guys think and what's the best approach to fix this. Thanks.
Cam chains can stretch. These adjustable sprockets can dial them in
(http://rpmracingca.com/prodimages/large/Head%20SCG-1.jpg)
http://rpmracingca.com/proddetail.asp?prod=Head%3ASCG&cat=39 (http://rpmracingca.com/proddetail.asp?prod=Head%3ASCG&cat=39)
This is definitely not the issue. Those are very close to the factory position. I may have proven in the past that if you let the cam chain jump during install the engine will still run with the intake cam 3 teeth off! Didn't run well, but did run well enough that a single tooth would be relatively minor compared to what you are describing.
In what gear and what speed and what RPM are you trying this 1/8 throttle "test"? It really sounds like you are lugging the engine and causing it to detonate. If this is not the case, then I'll bet a jelly donut you will need to go into the carbs again to get a proper job done (over the years, it seems like three times is the average!).
I'll admit it is hard to "diagnose" any running condition over the internet.
Please keep us posted on your progress!
Good luck!
Chris
I'm with Chris on this, the symptoms sound very much my bike with the ping-pong sound (spitting back through the carbs) and the engine "hunting" on a small throttle opening at a steady speed, after I cleaned out the carbs following a 7 year lay up. It took me 3 carb cleaning sessions to get it running as good as it does now.
I got my FJ carbs good in two sessions. My GN400 took me 6, and that was one carb. The low speed circuits have the smallest passages and are the hardest to get clean.
I'm pretty sure you are 1 tooth out, easily done when re-fitting the cam chain tensioner. I agree with the other's comments that
this will probably not be the cause of your low rev stumble. More than likely a carb issue with dirty pilot jets or mixture screws not adjusted properly.
Regards, Pete.
Robert at RPM rebuilt the carbs last year. I had this problem since I got the bike and after the carbs being rebuilt. It happens at any gear below 2000 rpm at low speeds. I took the carbs out of the bike today. I'm going to inspect them tomorrow. I will post after running the bike this weekend. Thanks.
I may coast down at 2000 rpms, but I don't usually ride much other than parking lots at that low of rpm. I definitely won't do it in anything above second - and am not trying to accelerate just on the throttle. I'd say a downshift (or two!) is in order.
As Chris says, the timing marks on the camshaft are not the issue. I have adjustable sprockets because I couldn't even see the marks, it made no difference to the way it ran after I installed them and dialling in the timing anyway.
I'm not sure what a "pingpong" sound is but spitting back out the carbies at low rpm under load is not uncommon and is the carbies.
At the end of a big day with all the fun roads behind me, I will often slow for small country towns and accelerate out the other side from the 50 kph speed limit without changing out of 5th. That's about 1500 rpm and it's as smooth as butter, no chattering. It will pull away in top gear from as low as 40 kph, which is the nationwide speed limit for roadworks and for which I adopt a similar approach late in the day.
From the limited info supplied, I'm going with carbies.
Noel
After cleaning the carbs yesterday,this is the noise I'm talking about.
Sorry. I can't post a video. It's not backfiring from the carburetor. It's a metallic sound, more like clank, clank every 2 or 3 seconds at steady low rpm throttle.
low RPM idle is noisy on the FJ, the starter chain tends to clatter and slap.
The camtiming looks in range the sound can be stretched starterchain or the jackshaft .Can also be clutch rattle .If you syncronize the carburetors the clutch rattle and jackshaft clunk will go away.
If you ride with a steady throttle and the engine is surging the pilotscrews on one or more carb is too lean. check the sparkplugs ...
Quote from: Starquest on October 31, 2020, 12:48:46 PM
Sorry. I can't post a video. It's not backfiring from the carburetor. It's a metallic sound, more like clank, clank every 2 or 3 seconds at steady low rpm throttle.
I still think it's carb related - mine did something that sounds exactly the same and thorough carb cleaning solved it.
Quote from: Starquest on October 31, 2020, 12:48:46 PM
Sorry. I can't post a video. It's not backfiring from the carburetor. It's a metallic sound, more like clank, clank every 2 or 3 seconds at steady low rpm throttle.
I think perhaps there is a bit of a misunderstanding of noise names. The
spitting that was referred to is not backfiring. Anyway, with each subsequent post it becomes a bit clearer and more of a certainty that it's carbies.
That clank every 2 or 3 seconds is most likely the drivetrain lash snatching when the engine momentarily falters. I have ridden many bikes that displayed these symptoms and the more you describe it the more certain I am that it's your carbies, as it would appear most others that have offered advice do.
Noel
You can see the video on YouTube under Yamaha fj 1200 clunk noise. I can't downloaded here, sorry.
this is the link if anyone wants to listen.
https://www.youtube.com/watch?v=2zJaJFVvim0 (https://www.youtube.com/watch?v=2zJaJFVvim0)
Thanks,Paul. I'm not very good with this staff.
That sounds like it popping through the carbs. Do you still have the airbox installed?
That would explain the muffled sound of the popping/backfire
That can be a result of the cam timing being off and/or the carbs are lean at that held throttle position without any load on the engine.
No. Dual uni pods. It's a metallic sound coming from the Franck. May be starter chain?
I have some wild guessings: if the carbs not syncronized the clutch can make a clunking sound or it can be the starterchain hitting the oiljetnozzle
or it can be the jackshaft hitting into side of crankcase or it can be the rear camchain rail jumping up and down because of a veak spring on the bolt holding it in place or it can be as simple as a lose exhaustbend .
After hearing the sound again I'm thinking maybe the cam chain tensioner has gone bad or maybe it sits upside down.
Try to use a long screwdriver and hold it to into your ear and listen.
Sorry. I was busy this week. When I checked the valve lash last time, the timing chain looked ok, despite the cam timing being off. I checked the carbs sync this week. Robert did it a good job bench sync the carbs. May be I try 42.5 pilots first. If that's not solving the problem, I will mess with the cam timing.