Power loss between 4000-5000 rpm when in gear

pleasant

pleasant

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I think this is a similar issue to one many people on the forum have had, but I couldn't find a post that exactly described my issue.

What will happen is that in the 3rd and 4th gears at about 40-50km/hr the engine will bog down, drop in tone, and lose power. Sometimes I can rev up and out of this to bring back power and if I use the clutch it will rev up just fine.

Outside of this power range the engine will run fine. I last cleaned the carbs back in November but the bike hasn't seen much riding in this time frame. Additionally the petcock on the bike was replaced by the PO with a gravity style one with a cone shaped in-line fuel filter. Additionally it appears that he coated the tank with a cream that seems to be peeling around the edges.

My hunch is that the fuel filter is getting clogged but I don't understand why this would only occur in that very specific power range.

Thanks in advance for the help

EDIT: I thought I should add that these problems are occurring after a period of riding heavy rain in Vancouver, so I'm wondering if water got in somewhere and now is mucking things up
 
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Gotten anywhere on this? Were you experiencing these symptoms before at all? Sounds like a carb issue to me--gummed up somewhere. Air filters clean?
 
Maybe have a look at your main jet to see if you have the correct size. Someone with a bit more knowledage might come and correct me but im pretty sure that the main takes over at around 4000 rpms.
 
Been very busy between work and school so I haven't had a chance to get the carbs off the bike yet, but I'm also considering it may be a fuel line or electrical issue as well. The petcock has been jerry rigged onto the tank in a very bizarre way and leaks all the time, plus I don't think my electrical system is working too well at all as my signals won't flash below 3000rpm most of the time.

I've also experienced a weird issue where I get a sudden speed boost at around 7000rpm where the bike will just take right off and bring me upwards of 100km/hr. This aspect leads me to believe it's a clog or issue in the carb, but I didn't think that there was another channel for that rpm range.
 
Just a few thoughts. I'm with Dave about the Diaphragms and your needles. Also you need to correct that petcock issue where it's been jerry-rigged. You mentioned there's a few electrical gremlins. As many of us have found our electricals are on the weak side. Most of these issues can be traced to poor connections. I would unplug all your connections 1 at a time for cleaning and see if that might also help with your trouble. Because if for some reason you have weak spark in that rpm range your engine will act sluggish this would also lead me to suspect your voltage regulator. Just thinking out loud!!!
 
Been thinking about this off & on. Some other things to think of is when you're in that rev range how smoothly is it running? I'm still thinking fuel delivery is the likely issue with diaphragms & needles as the most likely culprit but there's also a secondary fuel line between your carbs that may also need some attention. And before I forget swap out your fuel filter.
 
I just finished school so I'll have more time to work on the bike now.

I think you guys are on the money with it being a needle/jet issue, because I can get a LOT more power out of the bike in the higher rpms all of a sudden, like a boost or something. I'll take the carbs off next week.

Unfortunately now I have a whole new issue as well. I was riding at about 70km/h the other day and the bike stalled, locking the rear wheel up. Popped the clutch to start the bike again, pulled over, checked the oil and the crankcase appeared to be empty, which is bizarre because I hadn't noted any major leaks or burning. I stopped riding, brought back some oil and filled the bike up and rode home. Now when I run the engine though, there is what sounds like a metallic grinding or something. My friend speculates I may have blown a gasket, but I'm too not sure how to diagnose this issue.

Additionally this petcock is turning into a nightmare. Unfortunately it doesn't seem as simple as ordering a new vaccum petcock as it appears the PO modified the base of the gas tank to accept the thread in gravity petcock. I think they did a terrible job on the threading because the whole thing leaks/drips/weeps gas like crazy, which I'm also quite worried about as a safety issue directly above a hot engine. I'll take some pictures soon for the curious.
 
Sounds like you seized the motor. Running any engine without lubricating oil is a short path to destruction. Those infomercials for magic lubes that allow engines to run with no oil are pure BS (Slick50 and Lucas, I'm calling you out!) The damage to your engine has been done, nothing you can do about it now. The engine may last another year, or a day. All you can do is try it, but I'd expect it to die in short order.

If you want to try the engine, I'd suggest changing the oil and the filter again. Get a small rare earth magnet, 3mm diameter and 2 or 3 mm tall would be perfect, and stick it on the wet end of the oil drain plug before you reinstall the plug. If you get more than one magnet, you may also attach one or more to the oil filter. They are strong enough to not go anywhere, so don't worry about gluing them in place or anything like that (I've been doing this for a couple decades without issue). I'd bet that after running the engine for a little bit, the magnets will be covered in metal filings - they will look like wet fur. If the engine noise doesn't get worse, and the magnets don't keep accumulating filings, keep riding. When I worked in aviation, we used to joke that the metal filings on the magnets were fine, until you could read a part number. Then you had to do something about it!

Again, don't be surprised if the engine doesn't last long. It won't be cost effective to rebuild it either. I'd be shopping for another bike at this point.
 
would like to bring this thread back to life im having a similer issue
when riding my bike seems very sluggish between 4500 and about 7000 once i hit 7000 it is like a rocket ship checked plugs they seem brownish with a tiny bit
of white

LEFT PLUG
IMG_1238[1].JPG


RIGHT PLUG
IMG_1239[1].JPG
 
I would say those plugs are soot black. And are they the correct plug? They don't look like extended reach plugs, but that may just be the camera angle....
 
The plugs should be the following:
NGK DR8ES-L or DR8EIX (Irridium plugs)
Champion RA6HC

Gap set to 0.023" - 0.028"

Yes, sooty and black is rich. Ignore the center electrode colour on extended reach plugs. Instead, read the mixture from the metal body that is exposed to the combustion chamber.
 
any tuning help would be awsome i have be trying to tune this bike for a while it allways gets the best of me ... whats the easyest way to tune the carbs i am pretty sure im close i just cant dial it in another thing i checked the jets idle left and right are 45 and left high speed is 127.5 the right is 120 i thought the right was sopossed to be 117.5
 
i would love to have a 117.5 i was gonna go to hully gully and order one but if u got one i could steal i would love you for ever :p if u have one of thoughs washers that go in between the carb and the jet i would send u 21 virgins lol
 

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