Brand new. Starting work

[youngbiker]

I just received a 1971 cb750k from my grandfather. I'm 19 and he said he had it running before he stowed it away. one of the exhausts rusted through on the bottom corner and that's why he parked it and hasn't gotten around to fixing it. he's too old to ride anymore so he's giving it to me. It's been parking for about 10 years he said I'm going to fix it up all nice and i was just wondering if you have any tips/concerns that I'm not aware about. Thanks for all the help.

[youngbiker]

I downloaded the 69-78 shop manual but it only says it's for 750 and 750f's will that be a problem or is it so similar that it doesn't really matter?

[Re-run]

The large manual will contain all the addendums needed. It will focus on the K bikes as the f bikes didnt come out till 75.

[Tyler Jones]

how do i know what k model i have? k1-k8?

[Re-run]

What year it is will tell you. The K's march in line with the year. 71 = k1 72=k2 and so on.

[youngbiker]

Thanks. I love this forum. thank you so much for setting it up.

[youngbiker]

[Re-run]

If that is a pic of the bike you got, it is not a 71. That engine is a dohc which came out in 79. On the neck you should find the VIN plate. It will tell you the year for sure but I would guess 81.

[youngbiker]

you're right my grandpa had two bike but one was 71 one was 81 and he mixed up the years. we found the title  though and it's an 81. so what k series do i have? and he also had a cb750k shop manual from 79 to 82... i'm still going to download the right one this time but so far the one i've got hasn't been too bad...

[youngbiker]

oh and i was talking to my uncle and he said that if i got the 4 into 1 exhaust that it would increase performance. is that true?

[LukeM]

If you have the factory Honda manual for your bike, that's probably the same one that's found on this site. You could download it, just to compare.

Generally speaking, a 4 to 1 exhaust will give less back pressure, which results in more airflow (and noise  ) through the engine.  However, changing the back pressure means changing the jets and settings on the carbs to compensate. The SuperSport model of CB750 had different carbs from the factory, along with the 4 - 1 exhaust system, ostensibly to correct for this condition. At least that's what my Haynes manual says.

You've got the basis of a neat project there.  Hopefully you and your uncle can work on it together. I've enjoyed working on my sons' bikes, and that's how I ended up here with my own bike.

Luke

[Re-run]

Well a 4-1 will certainly save weight. No doubt about that. However, a 4-1 works better at higher speeds, you can actually lose a small amount of bottom end. You dont always have to rejet for a 4-1 but it depends on the model so it is possible. Luke is certainly right though about your project. Sounds like a good time.

[youngbiker]

yeah I really think so too. he has his own bike.... all my uncles besides two have their own bikes and i think it would be way fun once i've finished mine to go on a ride with them. my reason for asking about the 4 into 1 was not just about the power it was also about cost. i've looked it up and from what i've found there's a cheap 4 to 1 for 299.00 but for individual pipes seems more expensive. i'm only 19 and work at mcdonalds so i don't have the best financial situation and 3 of the pipes won't pass inspection. also that isn't going to be permanent. it'll just be temporary so i can afford to have it fixed this summer. i've already spent my whole check that i got on wednesday on fixing it up so it'll be about two weeks before i can do anything else to it besides de rusting/lining the gas tank which i'm planning on doing today.

[youngbiker]

and luke what jets are you talking about? i'm already planning on getting my carbs rebuilt or doing it myself after sitting for so long...

[Re-run]

Well I will throw up a couple ideas for you.

http://www.denniskirk.com/jsp/tpl/cmn/prodlist.jsp;jsessionid=TYXTVGIZQBV2XLA0WTVSM4VMDK0NCIV0?store=Main&category=403&np=&mmyId=7723

http://www.bikebandit.com/vance-hines-standard-pro-pipes?mg=994&t=1&td=1   (supposedly have to mod somewhere. Maybe do google on this system.)

http://www.bikebandit.com/mac-4-into-1-canister-system?mg=994&t=1&td=1

Check those out.

[youngbiker]

thanks for those. yeah i was looking at two in ones but the ones i could find were too expensive. does bike bandit usually have as good of deals as those??? and honestly i'm thinking about perusing a junkyard too. just see if i can find maybe one that already has a four in one that's not rusted through or maybe find a couple with ok ones. i just want to go with my cheapest options so i can get it passed inspection sooner. as soon as it's passed inspection then i can start spending real money on it. i just think it's more important to ride than to look pretty....

[Re-run]

Well ebay did have some pipes but of course that is a crap shoot as the pics might look good but you never know.
Otherwise bikebandit is usually not too bad.
Another cheap source is partsnmore.com No exhaust but a lot of other parts.