How To Measure Mikuni Carb Size

I. Introduction

If you own an old model motorcycle and you exercise non accept the user manual, there are chances that you will have difficulty identifying the parts, including the carburetor.

You merely know that it is fitted with a Mikuni carburetor and you want to know its code and size and whether it's a genuine Mikuni carburetor?

2. Mikuni Carburetor Identification

In this section, we will effort to detect the answers to the following questions:

How to know if your Mikuni carb is fake or original?
How to know which Mikuni carb you lot have?
How to identify Mikuni carb size?
How to observe the carburetor number?

[1] How to know your Mikuni carb is imitation or original?

Original or genuine Mikuni carburetors have a body of aluminum alloy die casting and you can see the markings 'MIKUNI CORP' and 'MADE IN JAPAN' very prominently on the torso (the markings are cast into the body).

If you have seen and handled a Mikuni carburetor earlier, you'll be easily able to differentiate the original from the fake past but taking the carburetor in your paw; ane clear cue tin can exist that the fake one will exist much lighter (otherwise, how tin can they be priced depression).

Our next question is how to place your Mikuni carburetor in terms of its size and code.

For this, y'all need to take out your carb from your motorcycle and clean and dry it. Y'all can do this yourself if yous have previous experience of handling carburetors or take the help of your mechanic.

[2] How to identify Mikuni carb size?

In the code or designation of a Mikuni carburetor like HSR 42 or TM 42, HSR or TM indicates the pattern of the carburetor and 42 indicates the bore (internal diameter) size (in mm) on the engine cease of the carburetor (your carburetor has ii ends, one end is connected to the engine (engine end) and the other terminate is connected to the air filter (air filter finish)).

Examine the engine stop of the carburetor and you may discover the stamped marker like HSR 42 or like to that which indicates the pattern and size of your carburetor.

If y'all do not detect any marking or if the marking is faded (using a crude brush for cleaning the outside of the carburetor may vesture out the markings), then yous accept to use a Vernier caliper or a good quality steel scale to measure the bore on the engine end in 'mm'; this gives you the size of the carburetor.

[3] How to know which Mikuni carb you have? How to find the carburetor number?

I have collected the information of Mikuni single carburetors of all designs (used in motorcycles) and sizes and compiled them in Table-ane below. This data is nerveless from the Mikuni catalog.

You can download the Mikuni catalog at this page

As per the itemize:

HSR 42, TM 42-6, and TM 42-6PK are the same, except the stop on the body, and similarly, HSR 45, TM 45-2K, and TM 45-two PK are the same except the stop on the torso.
As well, Mikuni HS xl and TM twoscore-6 are the same.

So subsequently measuring the bore on the engine cease, let united states consider the post-obit:

If the bore size is 48 mm, your carburetor number is HSR 48 since in that location is only one Mikuni carburetor with a 48 mm bore size (Tabular array-1).

Similarly, if the diameter size is 42 mm, you have Mikuni HSR 42 whereas a diameter size of 45 mm indicates an HSR 45.

What if the bore size is 38 mm, your Mikuni can be TMX 38-27 or TMX 38-18 or TM 38-85 or TM 38-86 or VM 38.
Do not worry, take your caliper again and measure the dimensions A, B, C, and D to discover the design lawmaking of your Mikuni. (Please see Table-ii, Tabular array-3, and Table-four for the details).

TABLE-1
MIKUNI CARBURETOR Serial AND CODE
HSR series	HSR 42	HSR 45	HSR 48
TM series	TM 42-6	TM 42-6PK	TM 45-2K	TM 45-2PK
HS Series	HS forty
TMX Series	TMX 35-1	TMX 38-27	TMX 38-xviii
TM Series	TM 24-8001	VM 28-418	TM 32-1	TM 33-8012	TM 34-2	TM 36-2	TM 36-68	TM 38-85	TM 38- 86	TM 40 -half dozen
VM Series	VM eighteen	VM xx	VM 22	VM 24	VM 26	VM xxx	VM 32	VM 34	VM 36	VM 38	VM 44

(This information is compiled from the Mikuni Catalog)

The following paragraphs give you lot a brief introduction about the unlike designs of Mikuni carbs used in motorcycles.

[iv] HSR Series Carburetors: 42, 45 and 48 mm smoothbore carburetors

Mikuni HSR Serial carburetors are used in Harley-Davidsons and American Big Twins. The numbers 42, 45, and 48 indicate the bore size at the engine finish, 42 mm, 45 mm, and 48 mm respectively.

HSR 48 is the preferred one for racing motorcycles. HSR serial has flat-slide throttle with roller bearings and accelerator pump.

HSR and TM carburetors are the same for the following sizes.

TM 42-6 is	HSR 42 mm carburetor with a standard finish.
TM42-6 PK is	HSR 42 mm carburetor with polishing on the outside surfaces.
TM 45-2K is	HSR 45 mm carburetor with a standard end.
TM45-ii PK is	HSR 45 mm carburetor with polishing on the outside surfaces.

[v] RS Serial Carburetors

Mikuni RS Series carburetors are designed and congenital for in-line four-cylinder engines of performance motorcycles and come up with radial flat slides for throttling. Mikuni RS series carburetors are available in sizes 34, 36, 38, and 40 mm.

Mikuni RS series carburetors accept push-pull type throttle assembly to assure positive endmost of the carburetor throttle slides for high-operation racing engines.

[6] Mikuni TMX/TMS Series Carburetors:

They are bachelor in sizes 35 and 38 mm.

Mikuni TMX serial carburetors employ apartment slide throttle in a smooth diameter venturi.

TMX serial carburetors of 35 mm diameter size are used for 125 cc race engines whereas 38 mm bore size is used for 250 cc race engines.

Mikuni carburetors

Tabular array-2
MODEL→	TMX 35-1	TMX 38-27	TMX 38-18
DIMENSION↓
A	40	44	47
B	76
C	164
D	62
Full width	76

(This information is compiled from the Mikuni Catalog. All dimensions are in mm)

[7] Mikuni TM Series Carburetors

Mikuni TM Serial carburetors accept flat slide throttles and are bachelor in sizes 24, 28, 32, 33, 34, 36, 38, and 40 mm.

Mikuni carburetors

Tabular array-3
Model no→	TM24-8001	VM28 -418	TM 32 -1	TM33- 8012	TM34- ii	TM 36- 2	TM 36- 68	TM 38- 85	TM 38- 86	TM forty- 6
Dimensions↓	TM24-8001	VM28 -418	TM 32 -1	TM33- 8012	TM34- ii	TM 36- 2	TM 36- 68	TM 38- 85	TM 38- 86	TM forty- 6
A	31	33	twoscore	40	40	43	42	47	43	44
B	75	82	83	93	83	100	100	100	100	100
C	145	135	160	160	160	170	176	170	170	165
D	44	44	58	50	58	62	54	62	62	55
Full width	76	76	78	105	78	75	78	75	75

(This information is compiled from the Mikuni Catalog. All dimensions are in mm)

[8] Mikuni VM series carburetors: They accept round slide throttle and are very popular for their application in the sport of motorcycling and ATV (All-terrain Vehicle). VM serial carburettors come in sizes 18, xx, 22, 24, 26, 30, 32, 34, 36, 38 and 44.

Mikuni carburetors

Tabular array-4
Model no→	VM 18	VM 20	VM 22	VM 24	VM 26	VM thirty	VM 32	VM 34	VM 36	VM 38	VM 44
Dimensions↓
A	Clamp-on 22 ID	Flange 50.eight Bolt CTR	Flange 49 Bolt CTR	35	35	forty			43		52
B	67	66	85	80	93	93	102	93	116
C	108	115	114	116	122	137	142	137	152	154	193
D	32	43	43	43	44	58			62		70
Total width	61	76.5	82	82	82	83			79

(This information is compiled from the Mikuni Catalog. All dimensions are in mm)

Mikuni has got Super BN series Carburetors peculiarly designed for high horsepower racing watercraft.

Iii. Is Mikuni a skilful carburetor?

Mikuni carburetors are the products of Mikuni Corporation, Nihon and they are in the field of carburetors and other automotive-related products for more than than 60 years. They are well known and are one of the leading manufacturers in this field.

Mikuni American Corporation is a subsidiary company of its parent company in Japan and has its offices/works at Chicago and McAllen (Texas) (www.mikuni.com). This subsidiary was formed in 1968.

Mikuni Carburetors in 'Aftermarket sales' are sold for off-road and racing purposes only. However, in that location may be some Mikuni carburetors supplied equally OEM (original equipment manufacturer) to motorcycle manufacturers for on-road and metropolis use.

Mikuni Carburetors which are not designated as C.A.R.B. (California Air Resource Board) cannot be fitted on motorcycles that are intended to be used in towns or on freeways in the country of California and other states with similar restrictions on pollution control.

IV. Determination

Mikuni carburetors are mainly sold and used for off-road ATVs and racing purposes merely. Considering of this, Mikuni carbs should be replaced or repaired by the authorized dealer of Mikuni or by an experienced mechanic trained in Mikuni carburetors.

Source: https://happywrench.com/mikuni-carburetor-identification/