Topic: DOHC and Sohc carb spacing the same?

[CB750R]

I have a line on some carbs that might suit my 836 build. Is the spacing the same for the DOHCs?

[dragracer]

No. DOHC engines are wider. Carbs won't interchange.

[CB750R]

No. DOHC engines are wider. Carbs won't interchange.

Ok thanks, glad I didn’t commit, was a set of CR29s for $600 which would’ve been a pretty nice saving over new.

[dragracer]

No. DOHC engines are wider. Carbs won't interchange.

Ok thanks, glad I didn’t commit, was a set of CR29s for $600 which would’ve been a pretty nice saving over new.

CRs do have an adjustable rack. You may be able to modify them to work but at $600, I would try to reset the stock carbs first. Unless you're racing the bike, the stock carb jetted properly would be best for an 836 in my opinion. Others can probably chime in with better details as far as jet size and clip location.

[gschuld]

I saw them. Jim Sawtell is selling them.  Great guy. CR29s are universal streetable Race carbs.  They can be re spaced to fit the sohc4 spacing easily.

George

[CB750R]

I saw them. Jim Sawtell is selling them.  Great guy. CR29s are universal streetable Race carbs.  They can be re spaced to fit the sohc4 spacing easily.

George

>

Think they’re sold already  missed a good opportunity to let the head I’m getting built some quality carbs

[gschuld]

In wouldn’t discount factory carbs.  A well tuned set of round top factory carbs can keep up with a very strong street gas compression 836 engine better than you might think.

Pic below is of a big effort custom chassis/tank/seat race bike.  Check out the carbs…

George

[CB750R]

In wouldn’t discount factory carbs.  A well tuned set of round top factory carbs can keep up with a very strong street gas compression 836 engine better than you might think.

Pic below is of a big effort custom chassis/tank/seat race bike.  Check out the carbs…

George

Hey good to know, I have the PD Cb750f2 carbs will see how it runs and jetting goes when I get it back together.

[MRieck]

If anything I'd go with the RS-34's....the CR's are a PITA especially with that cold start set up they have.

[CB750R]

If anything I'd go with the RS-34's....the CR's are a PITA especially with that cold start set up they have.

Thanks Mike,  sure would prefer easy starting and street manners vs WOT performance. Will see how fast the Visa gets pulled out as I try and jet the PDs I guess! 😂

[bear]

I would have to agree with Mike. I have run CR's for many years and aside from cold starts their low speed fuel delivery is not up to scratch for a road bike either.
There are much better alternatives out there these days.
I would also endorse George's opinion in that a SOHC750's std carb's can support a lot of mod's before the bike started crying out for after market carb's. 

[paul_cb836]

836 with mild head, cam, HM300s and CR29s. I have never had any problem with cold starts or low speed performance - in fact no problem with performance at any speed😀. I really like them, they really woke the bike up after standard carbs.

[sohc boy]

it can be done CB750R , need swap all shafts an linkages around to narrow them ,mine 836cc & 2 street bikes as well (836 & 900), throttle response was killer , have made up sets 38mm an 40mm for big motor ,but never hit the track

[newday777]

836 with mild head, cam, HM300s and CR29s. I have never had any problem with cold starts or low speed performance - in fact no problem with performance at any speed😀. I really like them, they really woke the bike up after standard carbs.

Where are you located and what is the cold temps you speak of?

[PeWe]

I could not resist to have a look for carbs.
My K6 had ported head, cam and 836 in the 80's.
 Carbs were Mikuni VM29 (smoothbores without acc pump).
The boots cracked very quick so back to K6 stock.

Bike did not run slower or accelerated worse with stock K6 carbs (raised needles 1 step plus way bigger main).
The smoothbores had a better response at midrange, surprise wheelies and wheel spins

I have later changed them to work with stock boots which I used 2014.
I'll reuse them next season if I'll get the engine together,  pull my stock K2 engine for another  stronger engine with more cc.

I searched for smoothbores on eBay. Horrible prices for those.
A much better set of carbs does not cost more, new!!
https://www.bikeside.de/MIKUNI-TMR32-flat-slide-carburetor-for-all-CB-750-Four-69-78

Options are stacks or filter adaptors for 54mm K&N Pods.
Stock CB750 throttle device with wires work fine after adding a nut with a cut to get it over the wire.

The only thing here is to filter the pilot air jet which I did last summer.
Plus change needles. 9D3-52 is better.
Mine had 9E11-52 which is too rich.

My smoothbores had a really good choke with quick start every time.

My K6  today with TMR32 with accpump make engine to always start direct on all 4. Dyna-S helps.

[CB750R]

I think I’ll hold off on a carb purchase until I see how the PDs are working. I have played with 2 different sets of pods, and settled on the ‘antipod’ Uni filter set made by a member here, plus had a Zrx1100 with big bore cams etc that I had to jet, so I’m familiar with the process of banging your head against a wall until your bike runs properly  . I also learned that cheating is awesome and had installed a wideband O2 sensor and gauge so I could see AFR on cruise vs WOT etc. I have plans of ordering a Hindle exhaust for my bike and will get a bung installed for the sensor, like I did with my ZRX.  Once the jetting is sorted I will remove the gauge and wiring and put a cap in the bung and save the gauge for next time.