Saving a 1980 750 twin.

Finally had the time to cut and buff the paint. The result is dead flat with no definition line over the stripes. I also put on the badges.Ive been tinkering with the wiring off and on for months and it is finished. I did a bit of driveway tuning learned about the one year specific pilot screws to this year. Rounded up the nessecary parts and it's synced and seems to run great. All that remains to sort is an axle and a license plate. The latter of which should be here ina week or so.

Nìiiiiiiiiiice !

Looking forward to all the photos when finished

Perhaps another BOTM

Great job

First ride was a reasonable success! its got just enough power to be pretty fun, the exhaust has a great tone to it. Not too loud at idle but pretty rowdy when you get on it. The brakes are fantastic. I rode it to my graduation and hooned around a bit there afterwards with my robes on, my parents think I'm crazy. I put about 70 miles on it yesterday.

The jetting is pretty close, think I may need to go one bigger on the main and down a notch on the needle. I'm running into what i think is fuel starvation. When I'm on the highway, after a several seconds of going WOT its starts to miss and wont accelerate anymore like its running out of gas. if i back off for a bit and cruise, it seems like the float bowls refill and I can go WOT for a bit again until it starts missing again. WOT pulls from a stop to 5th gear are no problem its the extended WOT at 60+ where it happens. I have a cheapo petcock, I'm wondering if its not passing fuel fast enough. suggestions?

Congrats on the bike and the graduation.

I took the Pingel off my kz1000. At the very least it makes routing the fuel lines WAY easier, and looks a lot better. Unfortunately it didn't solve the fuel starvation problem. I popped the gas cap open and rode it like that as well thinking maybe it wasn't venting properly but that had no change. I'm gonna pull the carbs off and inspect the fuel inlets and float valves. Scratching my head here. suggestions?

Bike looks awesome!!... truly in a class by itself. The definitive 750 twin tracker example!

I had a similar symptom once when doing some wideband test runs. The bike ran great for an hour or so, but then after awhile I started noticing that the carbs would suddenly go lean at speed and I would feel hesitation. I pulled over and noticed one of the bowl vent hoses had popped out from under the tank and was in the airstream behind my leg. I put it back in place and the problem went away. I wasn't sure that was the problem so I tested it by replicating it a few times. Sure enough, whenever the vent tube was behind my leg, the bike would eventually go lean and hesitate at sustained high speeds. If the vent tube was up under the tank in the dead air space (as the bike came from the factory), the bike ran fine. I'm not sure if the vent was pressurizing the bowl and preventing fuel from entering, or was somehow creating just enough vacuum to prevent enough fuel from going up through the jets.

A rough calculation will tell you if the petcock flows enough. If your bike goes 33 MPG (at the very worst case scenario) at 100 mph, it needs to flow a gallon in about 20 minutes. Although moving at 100 mph may have some air related effect on the flow.

loudhvx wrote: A rough calculation will tell you if the petcock flows enough.

Another way to estimate the required flow rate is to convert horsepower to GPH. Just guess a slightly optimistic HP number.

blog.cantonracingproducts.com/blog/how_t...ur_engines_fuel_flow

loudhvx wrote: Bike looks awesome!!... truly in a class by itself. The definitive 750 twin tracker example!

I had a similar symptom once when doing some wideband test runs. The bike ran great for an hour or so, but then after awhile I started noticing that the carbs would suddenly go lean at speed and I would feel hesitation. I pulled over and noticed one of the bowl vent hoses had popped out from under the tank and was in the airstream behind my leg. I put it back in place and the problem went away. I wasn't sure that was the problem so I tested it by replicating it a few times. Sure enough, whenever the vent tube was behind my leg, the bike would eventually go lean and hesitate at sustained high speeds. If the vent tube was up under the tank in the dead air space (as the bike came from the factory), the bike ran fine. I'm not sure if the vent was pressurizing the bowl and preventing fuel from entering, or was somehow creating just enough vacuum to prevent enough fuel from going up through the jets.

A rough calculation will tell you if the petcock flows enough. If your bike goes 33 MPG (at the very worst case scenario) at 100 mph, it needs to flow a gallon in about 20 minutes. Although moving at 100 mph may have some air related effect on the flow.

Thats interesting. Right now i have the vent tubes pulled back behind the engine case which has worked fine for me on several bikes. I already took apart the carbs and noticed the float valves were 2.0 I had some 2.5 so I swapped those out. I will try riding it first then try the vent hose. thanks for the replies.

Nice Work Doc! I like your hands on detail to custom one off parts!
Keep those machinist skills going and growing.
Hands on mechanical machinists are going to be a lost talent soon.
Any Fathers out here with a young teenager Sons? Get them interested in a Trades Degree or Trade school. They will have a great future, yea it's hard, dirty work.
But they are in high demand! JMO.
But, back to what I was going to post, just jumping in with some KZ 750 twins in the Buffalo, Area.
1 stock and 1 a bobber! I'm not into bobbers! But if I was, this is one that is cool as FK! Done well!
Sorry to but in, butt this way more people can see these 2 motorcycles
2 craigs ads:
buffalo.craigslist.org/mcy/d/78-kawasaki...twin/6584305250.html
rochester.craigslist.org/mcy/d/1976-kz-7...saki/6583738290.html

DoctoRot wrote:

loudhvx wrote: Bike looks awesome!!... truly in a class by itself. The definitive 750 twin tracker example!

I had a similar symptom once when doing some wideband test runs. The bike ran great for an hour or so, but then after awhile I started noticing that the carbs would suddenly go lean at speed and I would feel hesitation. I pulled over and noticed one of the bowl vent hoses had popped out from under the tank and was in the airstream behind my leg. I put it back in place and the problem went away. I wasn't sure that was the problem so I tested it by replicating it a few times. Sure enough, whenever the vent tube was behind my leg, the bike would eventually go lean and hesitate at sustained high speeds. If the vent tube was up under the tank in the dead air space (as the bike came from the factory), the bike ran fine. I'm not sure if the vent was pressurizing the bowl and preventing fuel from entering, or was somehow creating just enough vacuum to prevent enough fuel from going up through the jets.

A rough calculation will tell you if the petcock flows enough. If your bike goes 33 MPG (at the very worst case scenario) at 100 mph, it needs to flow a gallon in about 20 minutes. Although moving at 100 mph may have some air related effect on the flow.

Thats interesting. Right now i have the vent tubes pulled back behind the engine case which has worked fine for me on several bikes. I already took apart the carbs and noticed the float valves were 2.0 I had some 2.5 so I swapped those out. I will try riding it first then try the vent hose. thanks for the replies.

That's what I was thinking. With my 28's the bike would run great but going up the long hill in 5th it would seem to be running out of gas then recover after I was over the top. Went from 2.0 to 2.5 and that cured it.
Steve

thanks guys.
The 2.5 float valve solved the problem. it also richened everything else up and the bike is happier on the whole. Im thinking about switching them to a 2.8 just to ensure the float valve isn't acting as my main jet.

My question is; why would they install small float valves? wouldn't you want to have the biggest possible float valve to ensure fuel delivery, and let the jets do the fuel metering?

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