Topic: WTF?? 750k or F carbs and whats this hose...pics!!! jet stuff too...

[timdhawk]

the story: just bought a 78 750k a few weeks ago SUPPOSEDLY jetted for the pods and 4 into 1 exhaust (F style). some research i found has the jets as 105 for the K and 110 for the F. mine are 35 and 110. also some pics i found show the same style carbs but one with a throttle return spring from the carbs to the holding plate and another (the one i have) with a spring arond the shaft (see pic).

SO what cards do i have, am i jetted correctly and what is this little hose for with the bolt in it? its next to the fuel supply hose to the carbs?

[Deltarider]

I am not that familiar with 750's but it looks like either the PO went from two fuel lines to one, OR - if your petcock has two outlets - had an inline fuelfilter where the bolt is now.

[eurban]

Not quite Deltarider. The hose is a vent hose and should not be plugged with a screw.  Normally it has some sort of plastic restrictor in it. . .Actually, stock main jet specs for the 78s is 105 for the f and 110 for the K.  Download the entire factory manual here:  http://www.mediafire.com/?5ttzdg9yyuz
Reading it would be a good idea. . . .    Are you jetted correctly?  Can't say; the F2/F3 models (77/78) do indeed have a 4-1 exhaust but they also have larger intake valves, different size intake tubes, and a slightly lower compression engine. There are many types of 4-1 exhausts.  What type do you have?  It isn't good logic to assume that what works for a stock F3 will work for a K8 with a 4-1.

[timdhawk]

okay, since i have the K model, i have stock jets... so not "jetted" as PO stated. bummer...

this is the exhaust i have

 

looks like a F model header with a ??defuser?? or a really small muffler.

does that tube need to be open to air?

thanks for the link, i did look at that and thats where i got confused about which model carbs i have because of the return spring...

[TwoTired]

On the side of the carbs, you'll see a large PD cast into the housing body.  Below it are some stamped numbers and letters.  This is how you identify what bike the carbs came from.

From the information we have so far those carbs came from th 77 or 78 K model, assuming those 110 main jets were there when first sold.

However, knowing how the carbs were delivered, won't help much in finding the correct jetting and adjustments for POD use and that pitiful excuse for a muffler.

Better hope you have the 77 K carbs,  I think these still have adjustable slide needles.  As, it is unlikely that just a main jet change is going to restore mixtures to proper level.

[eurban]

The hose is vented to air with a plastic fitting on the end. Don't know if this fitting is designed to keep the end of the hose from collapsing or to restrict, but you are probably all right without it as this is not a vacuum hose. Your exhaust header looks like stock F but as TT mentions the "muffler" in non stock and will likely be louder than hell.  Tuning your carbs to your current setup will likely require you to learn a good bit and to spend a good amount of time reading the spark plugs after plug chops,  and taking the carbs on and off to make changes.  Returning to a stock airbox and installing a proper muffler on the F header might make dialing the carbs in easier. . .  If your carbs do not have the adjustable main jet needles (most 77s do) then you can use small washers to shim the needles to a richer setting.  Your springs look correct. . . .  Do you have confidence that the PO of the those carbs, cleaned and adjusted them properly? Or is that your job? Did he /she or you remove the pilots and properly clean them and the passages behind? (ignore the factory manual on this subject as the pressed in pilots can and need to be pulled out to be cleaned properly) Is the accelerator pump working?  Are the floats set properly?  Are the carbs bench synchronized?