Some noob questions about my 'new' 86 VFR750

Well it turns out my 750 is actually a 700, shows that you should always double check these things when you buy a vehicle. Still an ok deal? I don't really know what the discrepancy in value is between the two...

 

The 750's are more rare, I don't have actual production numbers to give you, not a whole lot of difference HP-wise between the two.

 

Yeah, i have no complaints power wise, just value wise. Although I suppose it's better that I have the less rare one... haha.

 

So I was out riding today and I was stopped at a stoplight on the highway, and decided to get on it to 50 mph. The power, at wot to 9000 rpm shifts, just seem kind of lacking, particularly when I was passed by a 200 horsepower vw tiguan who i guess thought I was trying to race him. I was under the impression that this bike should be pretty fast... Maybe my carbs seriously need adjusting... Or weren't adjusted when the exhaust was put on. I'm gonna check the air filter tomorrow, but the bike runs smooth, just doesn't feel like 500 lbs and 100 HP to me...

 

Whoa... Definitely something not right if you were passed by VW of any flavor between 0 and 50 (and that's all first gear, yes?). As a noob rider it should have scared the crap out of you if you whacked it wide open from a stop. Time to start going through everything on the bike.

 

He didn't pass me in first gear, but he was right behind me. But still... There's a sticker on it from jackal motorsports here in the springs, gonna see if they know anything about the bike... Maybe when I get paid ill go ahead and pay for a dyno pull

 

I bet it's got something to do with the supertrapps. My first bike was an 86 vfr700 with supertrapp exhaust and at first I thought it was really fast, but then after I got better at riding, I realized that it was waaay slower than it should be. Take a few discs out of the supertrapp. It will be quieter and more similar to the stock exhausts. If this changes how the bike performs for the better, then it needs carb cleaning/ rejetting, most likley because it was not done when the exhausts were installed. My bike actually was not running on all 4 cylinders, and because it was my first bike, i wasn't able to tell by listening to it that it wasn't running right. The final solution is not to leave the bike as it is, with less discs in the exhaust. It is to have the carbs cleaned and rejetted or do it yourself, depending on your mechanical ability.

 

Yeah, I work in a shop so I'll be doing most everything myself. I'll try taking some discs out, too much backpressure I guess? I'm used to turbo efi motors, so... Thanks for the input, I'll give it a shot.

 

Actually (if memory serves), more discs in the SuperTrap setup means less back pressure (and more noise). If your carbs are gummed up (likely) and you add back pressure by removing discs, the performance *might* improve. If the bike has been sitting, just bite the bullet, pull the rack, clean everything out. A little research will no doubt provide you with jetting info for that exhaust, so you might as well make the changes while you have the rack out. If you find that what you're looking for is a 'DynoJet Kit', shoot me a PM. I have a kit I'll be happy to part with for the right price.

 

Well I'll let you know, definitely going to clean the carbs, I took the tank off today and cleaned the filter (K&N) and checked to make sure the fuel was flowing alright and whatnot. I also checked resistance on most of the ignition components. Everything seemed fine except all 4 coils' primary terminal resistances were way out of spec. 40 ohm instead of about 3 according to the manual. I'm just gonna go ahead and change the oil and do the spark plugs. When I put the bike back together it ran a little rough, does seem to be hesitating a little bit. Maybe i'll throw a fuel filter in too. Wouldn't my best bet just be to dyno the bike and get the shop's recommendation for carb jetting? I'll let you know if I want that dynojet kit...

Also, is that hose in this picture (lower left one, from the carbs) supposed to be connected to anything or is it just a breather hose?

 

Whoah, you are running sans fuel filter? If you have ANY rust in your tank I can take a pretty good guess at your throttle response problems.
(Hint: your carbs have stuff in them and need a cleaning, and get a fuel filter on it!)

 

Haha, nooo. I just mean REPLACE the fuel filter. And the bike is responsive, just doesn't feel very fast. I cleaned the air filter and I think it may have helped a tiny bit. Can anyone tell me if getting 40 ohms between the ignition coil terminals is really that terrible? They're way out of spec, but they all test the same i'm not sure where to get new coils...