Topic: Fast StreetBike Build **Update**

[TurboD]

Work on my SOHC Honda Streetbike build is finally showing some signs of progress.

Right after Christmas I picked up a 77 750F that was a complete basket case, it was a bare frame and was in a number of boxes. My reason for getting it was to build a fast Honda turbo streetbike for fun. This project like all that I do, I do most if not all the work myself, and I am always keeping an eye on the budget. I like to take pride in the fact that I did the work and also a minimal amount of cash was spent in the process.

As long as there is an interest, I will post updates of progress.

The actual work on the bike itself has just really begun, I started out working on the head ("Low Buck Head project"), now that I am nearing the end with it I have turned my attention on the build of the bike.

Here are some pictures of a quick mockup, I just got the bike in rolling condition yesterday. So far I have raked the frame 6 degrees (Home Brew Rake), and installed All Balls tapered steering bearings. I took the stock swingarm and added 10 inches. I plan on using a rear wheel from a 92 GXSR 1100 and a front wheel from a 81 GS250.

Here are some pictures of what I have so far.

[EnginebyAdam]

Following this Good luck and always cool to see a budget build

[nccb]

after seeing your other thread this should be cool

[Jim F]

Just don't take as long to build yours as I did my turbo
I am interested in this build as well

Jim

[TurboD]

Thanks Guys. My goal is to have this one running by spring.

I am in the market for parts if anyone has something I can use, PM email or post.

I'm looking for a good deal on a 836 kit, studs main and cylinder, lockup clutch.

[dragracer]

That rake job turned out well.

[754]

10 inches is a lot , i ran 6 over for a lot of years. I am thinking of going back to 4.5 or 5
 Reasons, chain availability, and being able to park it easily and turn around while parking.
 What are you planning for pipes?i ran a high pipe, helped the ground clearance a lot, but hard to find one, unless you can make one.. Sorry, forgot you had said turbo.

[dragracer]

Don't forget the streeting dampner with that raked frontend!! 

[TurboD]

With 10 inches plus the rake shes right at 70 inches, I've been riding bikes in the 68-72 inch range for years. Now with the resent surge of Grudge racing around here, this bike looks like a stocker, some of the guys are up in the mid 80's.

Thanks Frank. Actually with the rake, I there should'nt be a need for a dampner, I only use them on bikes with little or no rake. This bike should ride like a Cadillac at 150.. Lol

 

[dragracer]

I guess I'm to used to setting up race bikes and a steering dampener is standard equipment for safety.

[TurboD]

The race bikes with rake are not the ones that will get you in trouble, its the street bikes without that are a handfull. Don't ask me how I know. 

[dragracer]

The race bikes with rake are not the ones that will get you in trouble, its the street bikes without that are a handfull. Don't ask me how I know. 

Yes, I've been through a tank slapped or two over time on stock  bikes I've raced in the past. I just make it a habit to install them on every thing I race.

[DustyRags]

In for the show! 

[TurboD]

Progress is going a little slow, I am assembling and organizing parts to get started. With this build being a turbo and I am shooting for a low compression (8 -9:1), the options for a low cost piston are limited. After some research I decided to go with a set on feebay from a seller Cruzin image, after reading a number of reviews on different forums, people for the most part are happy with them. At the cost they are a good buy, $120 + $25 shipping. I ordered them 3 days ago and they are here today, all the way from Japan.

These are a 836 kit with rings, wrist pins, circlips and head gasket. After close inspection they appear to be of good quality and the machining looks nice and clean, I see no reason why these are not as good as the original Honda pistons.

As said these are 836, so they are slightly heavier, (as might be expected) about 1 oz or 30 grams more.  They are basically a stock replacement for the K model, so I am hoping that with a F2 head I can keep the compression ratio in the area that I am wanting.

[EnginebyAdam]

Progress is going a little slow, I am assembling and organizing parts to get started. With this build being a turbo and I am shooting for a low compression (8 -9:1), the options for a low cost piston are limited. After some research I decided to go with a set on feebay from a seller Cruzin image, after reading a number of reviews on different forums, people for the most part are happy with them. At the cost they are a good buy, $120 + $25 shipping. I ordered them 3 days ago and they are here today, all the way from Japan.

These are a 836 kit with rings, wrist pins, circlips and head gasket. After close inspection they appear to be of good quality and the machining looks nice and clean, I see no reason why these are not as good as the original Honda pistons.

As said these are 836, so they are slightly heavier, (as might be expected) about 1 oz or 30 grams more.  They are basically a stock replacement for the K model, so I am hoping that with a F2 head I can keep the compression ratio in the area that I am wanting.

TurboD I have two sets of the Cruzin image pistons for my 985cc dohc, not built yet. The only trouble I had with them is the wrist pin bore was tight on the pin. Other than that they are a good quality piston and they weight pretty close, or at least the two sets I have do. They should work nicely for your build

[Don R]

 I agree they are oem quality, is that good enough for a turbo application? Just asking, not giving an opinion.  Harder to find, and lots more $$ but a set of forged pistons would be nice.
 I'd say it depends entirely on how hard you are going to run it.

[Jim F]

you need low compression pistons with a turbo app
I have MTC turbo pistons that are 7.1 compression for my turbo
I think that the normal 836 kits are 10.1 comp.

Jim

[Old Scrambler]

A few years ago I acquired an F2 with the 'wrong' (k-model) 836 piston kit...............it measured 8:1 for compression and was an OK ride as an NA bike.  I sold it to a friend for his turbo project. You could reduce compression by a combination of dressing the piston faces, seating the valves a little deeper, and adding a few thou to the base gasket.

[754]

Lathe some off the crowns, after checking thickness..

[TurboD]

Don I believe they will be fine, I have seen guys (myself included) hammer the crap out of the Kawasaki 750 turbos and not have problems. Look at what the modern sportbike guys are doing with turbos and nitrous on stock engines. Many in the race car circles now feel the cast can be just as strong as forged "until" something bad happens, and then they are less forgiving and more brittle and will break apart easier. In the big picture These are small pistons with short strokes, they don't begin to see the forces and loads that are seen in a big auto engine. I'm going to give them a try, I have been a performance "myth buster" and have thought outside the box my whole life, I'm not going to stop now. Hehe

I have yet to CC the head, but going off of numbers I have read, and some quick calculating, I feel the compression will be right around the 8:1 range. Once I can actually mock the engine up to check deck height, at that point I may play around with head and base gaskets to adjust.

[TurboD]

I have a little more done today. I got my cylinders back from being bored out. Normally If they are just a slight over bore I will do them myself, these being more I sent them out. I got them back in 2 days from a well respected shop here in Indy, all though they looked good, they were tight at the tops and had a half thousand (.0005) taper to the bottoms. I got my hone out and got them perfectly round and straight, I now have them right at 1 thousand (.001), they are all dead on now.

[Old Scrambler]

Turbo........My 2-cents..........I like to ask before changing what a pro's work indicates.  My info from Millennium Technologies and others indicates your cylinders were bored to spec and should retain that slight amount of squeeze at the top. I always send the pistons along and I get each bore matched to a specific piston. 

This does not mean that you have ruined your build.................but don't be surprised if you get a little smoke in your exhaust.

[TurboD]

Thanks for the input. When I picked the cylinders up, there was 0 clearance at the top and about a half thousand at the bottoms. This is clearly too tight for a performance engine, especially a turbo engine. The cylinder wall finish will have more to do with ring seating than anything else.

Along with the race car and bike engines that I have built over the past 30 years,  for about 10 years I mainly built 5 HP Briggs for kart racing, in that time I personally bored and honed nearly 1000 cylinders. I learned a lot during that time. Some of those things went against what I had been told about racing engines. My engines were the most reliable and fastest in the area, holding a number of wins, track records, and championships. Now ten years  since stopped building them, I still have racers wanting me to do work for them.

[kmb69]

+1 TurboD

The cylinders should be as round and straight as you can get them. Obviously, 0 is big trouble. The Honda Manual says minimum clearance should be .0004-.0016in.

[Don R]

 I built a briggs or two myself. JR. Dragsters. We didn't have all those pesky rules. We did run an outlaw WKA engine once when we broke one and needed a quick replacement. The kart guy couldn't sell it to his buddies. He didn't want them to see what ha had been beating them with.