MX FCR Project (Monster 750).

[koko64]

Well, we're in stage 3 lock down now, with breaches enforced by the police and penalties for non compliance. No travel except for essential services work, health needs, essential shopping, welfare checks, so no riding except for travel to work. Just the excuse to take the 750 off the road to complete the carb R&D and finish some suspension work. That settles it.

I had another attempt to mix n match parts to see if I could squeeze in the FCRs. To my surprise, the fat bodied MX carbs fitted with less aggravation than the slightly narrower slant bodied carbs. The MX carbs are wider, but a solid block in shape with less prickly protusions than the slant FCRs, which foul each other. The fit of the MX carbs was still nloody ugly, with insufficient margin to frame spars to be risked for any customer. VE's manifold boots are closer to 35 deg rather than the 45 deg boots I'm using and would give the extra clearance required, but its a bloody ugly fit nevertheless. If VE's carbs dont flood or starve when the bike ascends steep hills, then it may be a solution for me cramming the MX carbs in there. If not then Mikuni TM 36 or 38 carbs are a svelte option.

Today I had a long and informative discussion with a bloke from MikuniOz, the Aust distributor. The TM non pumper carbs appear to be a real option, and an economical solution for Monster owners. I raised the issue of tuning data and baseline jetting which is the main concern for me. MikuniOz said they would provide baseline jetting and tuning support in response to my feedback. The TM 36 carbs are 440 Aud a pair with 70 odd bucks for a Mikuni quick turn 2 into to 1 throttle plus two 45 deg boots to use on the stock manifolds. Probably around 600 bucks for the lot or 660 bucks with the TM38's.

In light of this I'm tempted to use the TM's, but as I've previously mentioned, would need to decide between the 36 or 38mm carbs. With no accelerator pump, I'm wary of using the 38mm carbs on a stock 750, despite the assurances of the Mikuni rep. I don't want to have to run very rich pilot and mid range circuits to compensate for no acc pump. I'm open to people's thoughts on this.

Anyway, if I can fudge it with these manifold boots, http://www.nichecycle.com/ncs/categories/carburetor/flanges-adapters/carb-holder-elbow.html,
I'll run the monstrous MX carbs. We'll see how VE goes.

[MonsterHPD]

Nice.
Personally, I would go for the 36s. If they are the same body as the 38s, you could always open them up if the urge overwhelms you.
You might have a problem with a quick-turn throttle on a twin-carb setup. I tried that on my round-throttle Mikuni 36s once upon a time and switched back pretty quickly since the throttle got soo heavy.
But maybe you are much stronger than I :-)

[koko64]

I tend to agree, as I was leaning towards the 36mm carbs. I hate carb bog.
The 750 has standard compression (I checked), and I assume, standard cams and valves. It only has Staintune slip on pipes and a light Kaemna flywheel. It runs very well and has good response but gets breathless when really asking for performance. CV carbs annoy me.

[greenmonster]

. but gets breathless when really asking for performance.

Time for 800 heads...

[koko64]

Stop it

I have 900 cams and valves..., in a box. I'm trying to ignore them, maybe down the track with hi comp pistons.

[koko64]

I decided to try the slant bodied carbs again. I transfered components between carbs like short choke knobs, float bowls, etc to reduce the protrusions of each carb to improve their clearance between the frame rails and each other. The carb positions are not reversable as one has wider throttle cam bracket and longer fuel inlet. Slipping my hand under the carbs allows activation of the lhs carb choke. The rhs carb choke is easily reached.
Chokes on, fuel tap on, hit the starter and it roars into life.

With much cursing and bloody mindedness the bastards fit.
20200404_222145 by Tony Kokonis, on Flickr

[koko64]

20200404_221833 by Tony Kokonis, on Flickr

It's bloody tight everywhere. The carbs slightly angled upwards would solve many issues. I feel really comfortable tuning these carbs and love their performance. I hope the Nichecycle boots VE is using work well.

[Pinion]

Congrats

[koko64]

Cheers.

20200404_222114 by Tony Kokonis, on Flickr

I would not fit these Keihin carbs to these Mikuni 45 deg manifold boots if doing this for a customer. Maybe the boots VE is using would work better. It's too much mucking around (labour) and with too many clearance issues.

Tuning and testing next.

[greenmonster]

    And now the synking begins....


Reminds me abit when I decided on converting FCR`s from a Kwak IL4,
thinking "How hard can it be?"
Turned out not too hard but lotsa fiddling. And cheap, since I sold the other two.

[ducpainter]

How sore is your forehead?

[koko64]

How sore is your forehead?

Smashed from my stubborness

   And now the synking begins....

That's the easy part. I enjoy it.

[l88m22vette]

Random thought, any interest in better coils? I'll completely admit to only putzing around since I'm new but they definitely helped with start up, idle, and response (Dyna green, 8mm wires, iridium plugs). I know you're trying to baseline them for what's common on customer bikes but just wondering.

[koko64]

You read my mind. Once I sort these carbs I'll fit some CCW Exactfit coils I have spare. I doubt I'll be selling them anytime soon.

The stock coils actually work really well, best oem I've seen. They have enough spark to fire the plug but not so much to overwhelm the old style copper core plug wires and arc out to the frame , (thought howie would appreciate that).
If I fit them, they'll need modern, well insulated plug wires or there'll be a miss at idle.

[koko64]

Tuned and synched the mothermake the beast with two backsers. 
Of course I allowed for the rear cylinder's bizarre S bend manifold which eccentuates having to choose where in the rpm range you want the greatest harmony. I sacrificed some synch at idle to get the best everywhere else, but the idle still sounded good to the ear so not bad.

Doing what I did by using carbs that had been single all their lives invites tuning issues like uneven component wear, strange synch baselines and different modifications. I spent four hours resolving all sorts of tuning gremlins, but finally found a decent setting. Idle knob cable length, synch setting, cable tension and assymetric manifolds all contributed idle tuning variables.